/*
 * A utility program for the Linux OS SCSI generic ("sg") device driver.
 * Copyright (C) 1999-2010 D. Gilbert and P. Allworth
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 *
 * This program is a specialization of the Unix "dd" command in which
 * one or both of the given files is a scsi generic device or a raw
 * device. A block size ('bs') is assumed to be 512 if not given. This
 * program complains if 'ibs' or 'obs' are given with some other value
 * than 'bs'. If 'if' is not given or 'if=-' then stdin is assumed. If
 * 'of' is not given or 'of=-' then stdout assumed.  Multipliers:
 *    'c','C'  *1       'b','B' *512      'k' *1024      'K' *1000
 *    'm' *(1024^2)     'M' *(1000^2)     'g' *(1024^3)  'G' *(1000^3)
 *
 * A non-standard argument "bpt" (blocks per transfer) is added to control
 * the maximum number of blocks in each transfer. The default value is 128.
 * For example if "bs=512" and "bpt=32" then a maximum of 32 blocks (16KB
 * in this case) are transferred to or from the sg device in a single SCSI
 * command.
 *
 * This version should compile with Linux sg drivers with version numbers
 * >= 30000 . This version uses queuing within the Linux sg driver.
 */

#define _XOPEN_SOURCE 500

#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
#include <limits.h>
#include <signal.h>
#include <poll.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>
#include <linux/major.h>
#include <sys/time.h>
typedef uint8_t u_char;   /* horrible, for scsi.h */
#include "sg_lib.h"
#include "sg_io_linux.h"
#include "sg_unaligned.h"


static char * version_str = "0.63 20190324";
/* resurrected from "0.55 20020509" */

#define DEF_BLOCK_SIZE 512
#define DEF_BLOCKS_PER_TRANSFER 128


#define SENSE_BUFF_LEN 32       /* Arbitrary, could be larger */
#define DEF_TIMEOUT 60000       /* 60,000 millisecs == 60 seconds */
#define S_RW_LEN 10             /* Use SCSI READ(10) and WRITE(10) */

#define SGP_READ10 0x28
#define SGP_WRITE10 0x2a
#define DEF_NUM_THREADS 4       /* actually degree of concurrency */
#define MAX_NUM_THREADS 1024

#ifndef RAW_MAJOR
#define RAW_MAJOR 255   /*unlikely value */
#endif

#define FT_OTHER 0              /* filetype other than sg or raw device */
#define FT_SG 1                 /* filetype is sg char device */
#define FT_RAW 2                /* filetype is raw char device */

#define QS_IDLE 0               /* ready to start a copy cycle */
#define QS_IN_STARTED 1         /* commenced read */
#define QS_IN_FINISHED 2        /* finished read, ready for write */
#define QS_OUT_STARTED 3        /* commenced write */

#define QS_IN_POLL 11
#define QS_OUT_POLL 12

#define STR_SZ 1024
#define INOUTF_SZ 512
#define EBUFF_SZ 512


struct request_element;

typedef struct request_collection
{       /* one instance visible to all threads */
    int infd;
    int skip;
    int in_type;
    int in_scsi_type;
    int in_blk;                 /* next block address to read */
    int in_count;               /* blocks remaining for next read */
    int in_done_count;          /* count of completed in blocks */
    int in_partial;
    int outfd;
    int seek;
    int out_type;
    int out_scsi_type;
    int out_blk;                /* next block address to write */
    int out_count;              /* blocks remaining for next write */
    int out_done_count;         /* count of completed out blocks */
    int out_partial;
    int bs;
    int bpt;
    int dio;
    int dio_incomplete;
    int sum_of_resids;
    int coe;
    int debug;
    int num_rq_elems;
    struct request_element * req_arr;
} Rq_coll;

typedef struct request_element
{       /* one instance per worker thread */
    int qstate;                 /* "QS" state */
    int infd;
    int outfd;
    int wr;
    int blk;
    int num_blks;
    uint8_t * buffp;
    uint8_t * alloc_bp;
    sg_io_hdr_t io_hdr;
    uint8_t cmd[S_RW_LEN];
    uint8_t sb[SENSE_BUFF_LEN];
    int bs;
    int dio;
    int dio_incomplete;
    int resid;
    int in_scsi_type;
    int out_scsi_type;
    int debug;
} Rq_elem;

static Rq_coll rcoll;
static struct pollfd in_pollfd_arr[MAX_NUM_THREADS];
static struct pollfd out_pollfd_arr[MAX_NUM_THREADS];
static int dd_count = -1;

static const char * sg_allow_dio = "/sys/module/sg/parameters/allow_dio";

static int sg_finish_io(int wr, Rq_elem * rep);


/* Returns the number of times 'ch' is found in string 's' given the
 * string's length. */
static int
num_chs_in_str(const char * s, int slen, int ch)
{
    int res = 0;

    while (--slen >= 0) {
        if (ch == s[slen])
            ++res;
    }
    return res;
}

static void
install_handler (int sig_num, void (*sig_handler) (int sig))
{
    struct sigaction sigact;
    sigaction (sig_num, NULL, &sigact);
    if (sigact.sa_handler != SIG_IGN)
    {
        sigact.sa_handler = sig_handler;
        sigemptyset (&sigact.sa_mask);
        sigact.sa_flags = 0;
        sigaction (sig_num, &sigact, NULL);
    }
}

static void
print_stats()
{
    int infull, outfull;

    if (0 != rcoll.out_count)
        fprintf(stderr, "  remaining block count=%d\n", rcoll.out_count);
    infull = dd_count - rcoll.in_done_count - rcoll.in_partial;
    fprintf(stderr, "%d+%d records in\n", infull, rcoll.in_partial);
    outfull = dd_count - rcoll.out_done_count - rcoll.out_partial;
    fprintf(stderr, "%d+%d records out\n", outfull, rcoll.out_partial);
}

static void
interrupt_handler(int sig)
{
    struct sigaction sigact;

    sigact.sa_handler = SIG_DFL;
    sigemptyset (&sigact.sa_mask);
    sigact.sa_flags = 0;
    sigaction (sig, &sigact, NULL);
    fprintf(stderr, "Interrupted by signal,");
    print_stats ();
    kill (getpid (), sig);
}

static void
siginfo_handler(int sig)
{
    fprintf(stderr, "Progress report, continuing ...\n");
    print_stats ();
    if (sig) { }        /* suppress unused warning */
}

static int
dd_filetype(const char * filename)
{
    struct stat st;

    if (stat(filename, &st) < 0)
        return FT_OTHER;
    if (S_ISCHR(st.st_mode)) {
        if (RAW_MAJOR == major(st.st_rdev))
            return FT_RAW;
        else if (SCSI_GENERIC_MAJOR == major(st.st_rdev))
            return FT_SG;
    }
    return FT_OTHER;
}

static void
usage()
{
    fprintf(stderr, "Usage: "
           "sgq_dd  [if=<infile>] [skip=<n>] [of=<ofile>] [seek=<n>] "
           "[bs=<num>]\n"
           "            [bpt=<num>] [count=<n>] [dio=0|1] [thr=<n>] "
           "[coe=0|1] [gen=<n>]\n"
           "            [time=0|1] [deb=<n>] [--version]\n"
           "         usually either 'if' or 'of' is a sg or raw device\n"
           " 'bpt' is blocks_per_transfer (default is 128)\n"
           " 'dio' is direct IO, 1->attempt, 0->indirect IO (def)\n"
           " 'thr' is number of queues, must be > 0, default 4, max 1024\n");
    fprintf(stderr, " 'coe' continue on sg error, 0->exit (def), "
           "1->zero + continue\n"
           " 'time' 0->no timing(def), 1->time plus calculate throughput\n"
           " 'gen' 0-> 1 file is special(def), 1-> any files allowed\n"
           " 'deb' is debug, 0->none (def), > 0->varying degrees of debug\n");
}

/* Returns -1 for error, 0 for nothing found, QS_IN_POLL or QS_OUT_POLL */
static int
do_poll(Rq_coll * clp, int timeout, int * req_indexp)
{
    int k, res;

    if (FT_SG == clp->out_type) {
        while (((res = poll(out_pollfd_arr, clp->num_rq_elems, timeout)) < 0)
               && (EINTR == errno))
            ;
        if (res < 0) {
            perror("poll error on output fds");
            return -1;
        }
        else if (res > 0) {
            for (k = 0; k < clp->num_rq_elems; ++k) {
                if (out_pollfd_arr[k].revents & POLLIN) {
                    if (req_indexp)
                        *req_indexp = k;
                    return QS_OUT_POLL;
                }
            }
        }
    }
    if (FT_SG == clp->in_type) {
        while (((res = poll(in_pollfd_arr, clp->num_rq_elems, timeout)) < 0)
               && (EINTR == errno))
            ;
        if (res < 0) {
            perror("poll error on input fds");
            return -1;
        }
        else if (res > 0) {
            for (k = 0; k < clp->num_rq_elems; ++k) {
                if (in_pollfd_arr[k].revents & POLLIN) {
                    if (req_indexp)
                        *req_indexp = k;
                    return QS_IN_POLL;
                }
            }
        }
    }
    return 0;
}


/* Return of 0 -> success, -1 -> failure, 2 -> try again */
static int
read_capacity(int sg_fd, int * num_sect, int * sect_sz)
{
    int res;
    uint8_t rc_cdb [10] = {0x25, 0, 0, 0, 0, 0, 0, 0, 0, 0};
    uint8_t rcBuff[64];
    uint8_t sense_b[64];
    sg_io_hdr_t io_hdr;

    memset(&io_hdr, 0, sizeof(sg_io_hdr_t));
    io_hdr.interface_id = 'S';
    io_hdr.cmd_len = sizeof(rc_cdb);
    io_hdr.mx_sb_len = sizeof(sense_b);
    io_hdr.dxfer_direction = SG_DXFER_FROM_DEV;
    io_hdr.dxfer_len = sizeof(rcBuff);
    io_hdr.dxferp = rcBuff;
    io_hdr.cmdp = rc_cdb;
    io_hdr.sbp = sense_b;
    io_hdr.timeout = DEF_TIMEOUT;

    if (ioctl(sg_fd, SG_IO, &io_hdr) < 0) {
        perror("read_capacity (SG_IO) error");
        return -1;
    }
    res = sg_err_category3(&io_hdr);
    if (SG_LIB_CAT_UNIT_ATTENTION == res)
        return 2; /* probably have another go ... */
    else if (SG_LIB_CAT_CLEAN != res) {
        sg_chk_n_print3("read capacity", &io_hdr, 1);
        return -1;
    }
    *num_sect = 1 + sg_get_unaligned_be32(rcBuff + 0);
    *sect_sz = sg_get_unaligned_be32(rcBuff + 4);
#ifdef DEBUG
    fprintf(stderr, "number of sectors=%d, sector size=%d\n",
            *num_sect, *sect_sz);
#endif
    return 0;
}

/* 0 -> ok, 1 -> short read, -1 -> error */
static int
normal_in_operation(Rq_coll * clp, Rq_elem * rep, int blocks)
{
    int res;
    int stop_after_write = 0;

    rep->qstate = QS_IN_STARTED;
    if (rep->debug > 8)
        fprintf(stderr, "normal_in_operation: start blk=%d num_blks=%d\n",
                rep->blk, rep->num_blks);
    while (((res = read(rep->infd, rep->buffp,
                        blocks * rep->bs)) < 0) && (EINTR == errno))
        ;
    if (res < 0) {
        fprintf(stderr, "sgq_dd: reading, in_blk=%d, errno=%d\n", rep->blk,
                errno);
        return -1;
    }
    if (res < blocks * rep->bs) {
        int o_blocks = blocks;
        stop_after_write = 1;
        blocks = res / rep->bs;
        if ((res % rep->bs) > 0) {
            blocks++;
            clp->in_partial++;
        }
        /* Reverse out + re-apply blocks on clp */
        clp->in_blk -= o_blocks;
        clp->in_count += o_blocks;
        rep->num_blks = blocks;
        clp->in_blk += blocks;
        clp->in_count -= blocks;
    }
    clp->in_done_count -= blocks;
    rep->qstate = QS_IN_FINISHED;
    return stop_after_write;
}

/* 0 -> ok, -1 -> error */
static int
normal_out_operation(Rq_coll * clp, Rq_elem * rep, int blocks)
{
    int res;

    rep->qstate = QS_OUT_STARTED;
    if (rep->debug > 8)
        fprintf(stderr, "normal_out_operation: start blk=%d num_blks=%d\n",
                rep->blk, rep->num_blks);
    while (((res = write(rep->outfd, rep->buffp,
                 rep->num_blks * rep->bs)) < 0) && (EINTR == errno))
        ;
    if (res < 0) {
        fprintf(stderr, "sgq_dd: output, out_blk=%d, errno=%d\n", rep->blk,
                errno);
        return -1;
    }
    if (res < blocks * rep->bs) {
        blocks = res / rep->bs;
        if ((res % rep->bs) > 0) {
            blocks++;
            clp->out_partial++;
        }
        rep->num_blks = blocks;
    }
    clp->out_done_count -= blocks;
    rep->qstate = QS_IDLE;
    return 0;
}

/* Returns 1 for retryable, 0 for ok, -ve for error */
static int
sg_fin_in_operation(Rq_coll * clp, Rq_elem * rep)
{
    int res;

    rep->qstate = QS_IN_FINISHED;
    res = sg_finish_io(rep->wr, rep);
    if (res < 0) {
        if (clp->coe) {
            memset(rep->buffp, 0, rep->num_blks * rep->bs);
            fprintf(stderr, ">> substituted zeros for in blk=%d for "
                    "%d bytes\n", rep->blk, rep->num_blks * rep->bs);
            res = 0;
        }
        else {
            fprintf(stderr, "error finishing sg in command\n");
            return res;
        }
    }
    if (0 == res) { /* looks good, going to return */
        if (rep->dio_incomplete || rep->resid) {
            clp->dio_incomplete += rep->dio_incomplete;
            clp->sum_of_resids += rep->resid;
        }
        clp->in_done_count -= rep->num_blks;
    }
    return res;
}

/* Returns 1 for retryable, 0 for ok, -ve for error */
static int
sg_fin_out_operation(Rq_coll * clp, Rq_elem * rep)
{
    int res;

    rep->qstate = QS_IDLE;
    res = sg_finish_io(rep->wr, rep);
    if (res < 0) {
        if (clp->coe) {
            fprintf(stderr, ">> ignored error for out blk=%d for "
                    "%d bytes\n", rep->blk, rep->num_blks * rep->bs);
            res = 0;
        }
        else {
            fprintf(stderr, "error finishing sg out command\n");
            return res;
        }
    }
    if (0 == res) {
        if (rep->dio_incomplete || rep->resid) {
            clp->dio_incomplete += rep->dio_incomplete;
            clp->sum_of_resids += rep->resid;
        }
        clp->out_done_count -= rep->num_blks;
    }
    return res;
}

static int
sg_start_io(Rq_elem * rep)
{
    sg_io_hdr_t * hp = &rep->io_hdr;
    int res;

    rep->qstate = rep->wr ? QS_OUT_STARTED : QS_IN_STARTED;
    memset(rep->cmd, 0, sizeof(rep->cmd));
    rep->cmd[0] = rep->wr ? SGP_WRITE10 : SGP_READ10;
    sg_put_unaligned_be32((uint32_t)rep->blk, rep->cmd + 2);
    sg_put_unaligned_be16((uint16_t)rep->num_blks, rep->cmd + 7);
    memset(hp, 0, sizeof(sg_io_hdr_t));
    hp->interface_id = 'S';
    hp->cmd_len = sizeof(rep->cmd);
    hp->cmdp = rep->cmd;
    hp->dxfer_direction = rep->wr ? SG_DXFER_TO_DEV : SG_DXFER_FROM_DEV;
    hp->dxfer_len = rep->bs * rep->num_blks;
    hp->dxferp = rep->buffp;
    hp->mx_sb_len = sizeof(rep->sb);
    hp->sbp = rep->sb;
    hp->timeout = DEF_TIMEOUT;
    hp->usr_ptr = rep;
    hp->pack_id = rep->blk;
    if (rep->dio)
        hp->flags |= SG_FLAG_DIRECT_IO;
    if (rep->debug > 8) {
        fprintf(stderr, "sg_start_io: SCSI %s, blk=%d num_blks=%d\n",
               rep->wr ? "WRITE" : "READ", rep->blk, rep->num_blks);
        sg_print_command(hp->cmdp);
        fprintf(stderr, " len=%d, dxfrp=%p, cmd_len=%d\n",
                hp->dxfer_len, hp->dxferp, hp->cmd_len);
    }

    while (((res = write(rep->wr ? rep->outfd : rep->infd, hp,
                         sizeof(sg_io_hdr_t))) < 0) && (EINTR == errno))
        ;
    if (res < 0) {
        if (ENOMEM == errno)
            return 1;
        return res;
    }
    return 0;
}

/* -1 -> unrecoverable error, 0 -> successful, 1 -> try again */
static int
sg_finish_io(int wr, Rq_elem * rep)
{
    int res;
    sg_io_hdr_t io_hdr;
    sg_io_hdr_t * hp;
#if 0
    static int testing = 0;     /* thread dubious! */
#endif

    memset(&io_hdr, 0 , sizeof(sg_io_hdr_t));
    /* FORCE_PACK_ID active set only read packet with matching pack_id */
    io_hdr.interface_id = 'S';
    io_hdr.dxfer_direction = rep->wr ? SG_DXFER_TO_DEV : SG_DXFER_FROM_DEV;
    io_hdr.pack_id = rep->blk;

    while (((res = read(wr ? rep->outfd : rep->infd, &io_hdr,
                        sizeof(sg_io_hdr_t))) < 0) && (EINTR == errno))
        ;
    if (res < 0) {
        perror("finishing io on sg device, error");
        return -1;
    }
    if (rep != (Rq_elem *)io_hdr.usr_ptr) {
        fprintf(stderr,
                "sg_finish_io: bad usr_ptr, request-response mismatch\n");
        exit(1);
    }
    memcpy(&rep->io_hdr, &io_hdr, sizeof(sg_io_hdr_t));
    hp = &rep->io_hdr;

    switch (sg_err_category3(hp)) {
        case SG_LIB_CAT_CLEAN:
            break;
        case SG_LIB_CAT_RECOVERED:
            fprintf(stderr, "Recovered error on block=%d, num=%d\n",
                    rep->blk, rep->num_blks);
            break;
        case SG_LIB_CAT_UNIT_ATTENTION:
            return 1;
        default:
            {
                char ebuff[EBUFF_SZ];
                snprintf(ebuff, EBUFF_SZ, "%s blk=%d",
                         rep->wr ? "writing": "reading", rep->blk);
                sg_chk_n_print3(ebuff, hp, 1);
                return -1;
            }
    }
#if 0
    if (0 == (++testing % 100)) return -1;
#endif
    if (rep->dio &&
        ((hp->info & SG_INFO_DIRECT_IO_MASK) != SG_INFO_DIRECT_IO))
        rep->dio_incomplete = 1; /* count dios done as indirect IO */
    else
        rep->dio_incomplete = 0;
    rep->resid = hp->resid;
    if (rep->debug > 8)
        fprintf(stderr, "sg_finish_io: completed %s, blk=%d\n",
                wr ? "WRITE" : "READ", rep->blk);
    return 0;
}

/* Returns scsi_type or -1 for error */
static int
sg_prepare(int fd, int sz)
{
    int res, t;
    struct sg_scsi_id info;

    res = ioctl(fd, SG_GET_VERSION_NUM, &t);
    if ((res < 0) || (t < 30000)) {
        fprintf(stderr, "sgq_dd: sg driver prior to 3.x.y\n");
        return -1;
    }
    res = ioctl(fd, SG_SET_RESERVED_SIZE, &sz);
    if (res < 0)
        perror("sgq_dd: SG_SET_RESERVED_SIZE error");
#if 0
    t = 1;
    res = ioctl(fd, SG_SET_FORCE_PACK_ID, &t);
    if (res < 0)
        perror("sgq_dd: SG_SET_FORCE_PACK_ID error");
#endif
    res = ioctl(fd, SG_GET_SCSI_ID, &info);
    if (res < 0) {
        perror("sgq_dd: SG_SET_SCSI_ID error");
        return -1;
    }
    else
        return info.scsi_type;
}

/* Return 0 for ok, anything else for errors */
static int
prepare_rq_elems(Rq_coll * clp, const char * inf, const char * outf)
{
    int k;
    Rq_elem * rep;
    size_t psz;
    char ebuff[EBUFF_SZ];
    int sz = clp->bpt * clp->bs;
    int scsi_type;

    clp->req_arr = malloc(sizeof(Rq_elem) * clp->num_rq_elems);
    if (NULL == clp->req_arr)
        return 1;
    for (k = 0; k < clp->num_rq_elems; ++k) {
        rep = &clp->req_arr[k];
        memset(rep, 0, sizeof(Rq_elem));
        psz = getpagesize();
        if (NULL == (rep->alloc_bp = malloc(sz + psz)))
            return 1;
        rep->buffp = (uint8_t *)
                (((unsigned long)rep->alloc_bp + psz - 1) & (~(psz - 1)));
        rep->qstate = QS_IDLE;
        rep->bs = clp->bs;
        rep->dio = clp->dio;
        rep->debug = clp->debug;
        rep->out_scsi_type = clp->out_scsi_type;
        if (FT_SG == clp->in_type) {
            if (0 == k)
                rep->infd = clp->infd;
            else {
                if ((rep->infd = open(inf, O_RDWR)) < 0) {
                    snprintf(ebuff, EBUFF_SZ,
                             "sgq_dd: could not open %s for sg reading", inf);
                    perror(ebuff);
                    return 1;
                }
            }
            in_pollfd_arr[k].fd = rep->infd;
            in_pollfd_arr[k].events = POLLIN;
            if ((scsi_type = sg_prepare(rep->infd, sz)) < 0)
                return 1;
            if (0 == k)
                clp->in_scsi_type = scsi_type;
            rep->in_scsi_type = clp->in_scsi_type;
        }
        else
            rep->infd = clp->infd;

        if (FT_SG == clp->out_type) {
            if (0 == k)
                rep->outfd = clp->outfd;
            else {
                if ((rep->outfd = open(outf, O_RDWR)) < 0) {
                    snprintf(ebuff, EBUFF_SZ,
                             "sgq_dd: could not open %s for sg writing", outf);
                    perror(ebuff);
                    return 1;
                }
            }
            out_pollfd_arr[k].fd = rep->outfd;
            out_pollfd_arr[k].events = POLLIN;
            if ((scsi_type = sg_prepare(rep->outfd, sz)) < 0)
                return 1;
            if (0 == k)
                clp->out_scsi_type = scsi_type;
            rep->out_scsi_type = clp->out_scsi_type;
        }
        else
            rep->outfd = clp->outfd;
    }
    return 0;
}

/* Returns a "QS" code and req index, or QS_IDLE and position of first idle
   (-1 if no idle position). Returns -1 on poll error. */
static int
decider(Rq_coll * clp, int first_xfer, int * req_indexp)
{
    int k, res;
    Rq_elem * rep;
    int first_idle_index = -1;
    int lowest_blk_index = -1;
    int times;
    int try_poll = 0;
    int lowest_blk = INT_MAX;

    times = first_xfer ? 1 : clp->num_rq_elems;
    for (k = 0; k < times; ++k) {
        rep = &clp->req_arr[k];
        if ((QS_IN_STARTED == rep->qstate) ||
            (QS_OUT_STARTED == rep->qstate))
            try_poll = 1;
        else if ((QS_IN_FINISHED == rep->qstate) && (rep->blk < lowest_blk)) {
            lowest_blk = rep->blk;
            lowest_blk_index = k;
        }
        else if ((QS_IDLE == rep->qstate) && (first_idle_index < 0))
            first_idle_index = k;
    }
    if (try_poll) {
        res = do_poll(clp, 0, req_indexp);
        if (0 != res)
            return res;
    }

    if (lowest_blk_index >= 0) {
        if (req_indexp)
            *req_indexp = lowest_blk_index;
        return QS_IN_FINISHED;
    }
#if 0
    if (try_poll) {
        res = do_poll(clp, 2, req_indexp);
        if (0 != res)
            return res;
    }
#endif
    if (req_indexp)
        *req_indexp = first_idle_index;
    return QS_IDLE;
}


int
main(int argc, char * argv[])
{
    bool verbose_given = false;
    bool version_given = false;
    int skip = 0;
    int seek = 0;
    int ibs = 0;
    int obs = 0;
    char str[STR_SZ];
    char * key;
    char * buf;
    char inf[INOUTF_SZ];
    char outf[INOUTF_SZ];
    int res, k, n, keylen;
    int in_num_sect = 0;
    int out_num_sect = 0;
    int num_threads = DEF_NUM_THREADS;
    int gen = 0;
    int do_time = 0;
    int in_sect_sz, out_sect_sz, first_xfer, qstate, req_index, seek_skip;
    int blocks, stop_after_write, terminate;
    char ebuff[EBUFF_SZ];
    Rq_elem * rep;
    struct timeval start_tm, end_tm;

    memset(&rcoll, 0, sizeof(Rq_coll));
    rcoll.bpt = DEF_BLOCKS_PER_TRANSFER;
    rcoll.in_type = FT_OTHER;
    rcoll.out_type = FT_OTHER;
    inf[0] = '\0';
    outf[0] = '\0';

    for(k = 1; k < argc; k++) {
        if (argv[k])
            strncpy(str, argv[k], STR_SZ);
        else
            continue;
        for(key = str, buf = key; *buf && *buf != '=';)
            buf++;
        if (*buf)
            *buf++ = '\0';
        keylen = strlen(key);
        if (strcmp(key,"if") == 0)
            strncpy(inf, buf, INOUTF_SZ);
        else if (strcmp(key,"of") == 0)
            strncpy(outf, buf, INOUTF_SZ);
        else if (0 == strcmp(key,"ibs"))
            ibs = sg_get_num(buf);
        else if (0 == strcmp(key,"obs"))
            obs = sg_get_num(buf);
        else if (0 == strcmp(key,"bs"))
            rcoll.bs = sg_get_num(buf);
        else if (0 == strcmp(key,"bpt"))
            rcoll.bpt = sg_get_num(buf);
        else if (0 == strcmp(key,"skip"))
            skip = sg_get_num(buf);
        else if (0 == strcmp(key,"seek"))
            seek = sg_get_num(buf);
        else if (0 == strcmp(key,"count"))
            dd_count = sg_get_num(buf);
        else if (0 == strcmp(key,"dio"))
            rcoll.dio = sg_get_num(buf);
        else if (0 == strcmp(key,"thr"))
            num_threads = sg_get_num(buf);
        else if (0 == strcmp(key,"coe"))
            rcoll.coe = sg_get_num(buf);
        else if (0 == strcmp(key,"gen"))
            gen = sg_get_num(buf);
        else if ((0 == strncmp(key,"deb", 3)) || (0 == strncmp(key,"verb", 4)))
            rcoll.debug = sg_get_num(buf);
        else if (0 == strcmp(key,"time"))
            do_time = sg_get_num(buf);
        else if ((keylen > 1) && ('-' == key[0]) && ('-' != key[1])) {
            res = 0;
            n = num_chs_in_str(key + 1, keylen - 1, 'h');
            if (n > 0) {
                usage();
                return 0;
            }
            n = num_chs_in_str(key + 1, keylen - 1, 'v');
            if (n > 0)
                verbose_given = true;
            rcoll.debug += n;
            res += n;
            n = num_chs_in_str(key + 1, keylen - 1, 'V');
            if (n > 0)
                version_given = true;
            res += n;
            if (res < (keylen - 1)) {
                fprintf(stderr, "Unrecognised short option in '%s', try "
                        "'--help'\n", key);
                return SG_LIB_SYNTAX_ERROR;
            }
        } else if (0 == strncmp(key, "--help", 6)) {
            usage();
            return 0;
        } else if (0 == strncmp(key, "--verb", 6)) {
            verbose_given = true;
            ++rcoll.debug;
        } else if (0 == strncmp(key, "--vers", 6))
            version_given = true;
        else {
            fprintf(stderr, "Unrecognized argument '%s'\n", key);
            usage();
            return 1;
        }
    }
#ifdef DEBUG
    fprintf(stderr, "In DEBUG mode, ");
    if (verbose_given && version_given) {
        fprintf(stderr, "but override: '-vV' given, zero verbose and "
                "continue\n");
        verbose_given = false;
        version_given = false;
        rcoll.debug = 0;
    } else if (! verbose_given) {
        fprintf(stderr, "set '-vv'\n");
        rcoll.debug = 2;
    } else
        fprintf(stderr, "keep verbose=%d\n", rcoll.debug);
#else
    if (verbose_given && version_given)
        fprintf(stderr, "Not in DEBUG mode, so '-vV' has no special action\n");
#endif
    if (version_given) {
        fprintf(stderr, "sgq_dd for sg version 3 driver: %s\n",
                version_str);
            return 0;
        return 0;
    }

    if (argc < 2) {
        usage();
        return 1;
    }
    if (rcoll.bs <= 0) {
        rcoll.bs = DEF_BLOCK_SIZE;
        fprintf(stderr, "Assume default 'bs' (block size) of %d bytes\n",
                rcoll.bs);
    }
    if ((ibs && (ibs != rcoll.bs)) || (obs && (obs != rcoll.bs))) {
        fprintf(stderr, "If 'ibs' or 'obs' given must be same as 'bs'\n");
        usage();
        return 1;
    }
    if ((skip < 0) || (seek < 0)) {
        fprintf(stderr, "skip and seek cannot be negative\n");
        return 1;
    }
    if ((num_threads < 1) || (num_threads > MAX_NUM_THREADS)) {
        fprintf(stderr, "too few or too many threads requested\n");
        usage();
        return 1;
    }
    if (rcoll.debug)
        fprintf(stderr, "sgq_dd: if=%s skip=%d of=%s seek=%d count=%d\n",
               inf, skip, outf, seek, dd_count);
    install_handler (SIGINT, interrupt_handler);
    install_handler (SIGQUIT, interrupt_handler);
    install_handler (SIGPIPE, interrupt_handler);
    install_handler (SIGUSR1, siginfo_handler);

    rcoll.infd = STDIN_FILENO;
    rcoll.outfd = STDOUT_FILENO;
    if (inf[0] && ('-' != inf[0])) {
        rcoll.in_type = dd_filetype(inf);

        if (FT_SG == rcoll.in_type) {
            if ((rcoll.infd = open(inf, O_RDWR)) < 0) {
                snprintf(ebuff, EBUFF_SZ,
                         "sgq_dd: could not open %s for sg reading", inf);
                perror(ebuff);
                return 1;
            }
        }
        if (FT_SG != rcoll.in_type) {
            if ((rcoll.infd = open(inf, O_RDONLY)) < 0) {
                snprintf(ebuff, EBUFF_SZ,
                         "sgq_dd: could not open %s for reading", inf);
                perror(ebuff);
                return 1;
            }
            else if (skip > 0) {
                loff_t offset = skip;

                offset *= rcoll.bs;       /* could exceed 32 here! */
                if (lseek(rcoll.infd, offset, SEEK_SET) < 0) {
                    snprintf(ebuff, EBUFF_SZ,
                "sgq_dd: couldn't skip to required position on %s", inf);
                    perror(ebuff);
                    return 1;
                }
            }
        }
    }
    if (outf[0] && ('-' != outf[0])) {
        rcoll.out_type = dd_filetype(outf);

        if (FT_SG == rcoll.out_type) {
            if ((rcoll.outfd = open(outf, O_RDWR)) < 0) {
                snprintf(ebuff, EBUFF_SZ,
                        "sgq_dd: could not open %s for sg writing", outf);
                perror(ebuff);
                return 1;
            }
        }
        else {
            if (FT_OTHER == rcoll.out_type) {
                if ((rcoll.outfd = open(outf, O_WRONLY | O_CREAT, 0666)) < 0) {
                    snprintf(ebuff, EBUFF_SZ,
                            "sgq_dd: could not open %s for writing", outf);
                    perror(ebuff);
                    return 1;
                }
            }
            else {
                if ((rcoll.outfd = open(outf, O_WRONLY)) < 0) {
                    snprintf(ebuff, EBUFF_SZ,
                            "sgq_dd: could not open %s for raw writing", outf);
                    perror(ebuff);
                    return 1;
                }
            }
            if (seek > 0) {
                loff_t offset = seek;

                offset *= rcoll.bs;       /* could exceed 32 bits here! */
                if (lseek(rcoll.outfd, offset, SEEK_SET) < 0) {
                    snprintf(ebuff, EBUFF_SZ,
                "sgq_dd: couldn't seek to required position on %s", outf);
                    perror(ebuff);
                    return 1;
                }
            }
        }
    }
    if ((STDIN_FILENO == rcoll.infd) && (STDOUT_FILENO == rcoll.outfd)) {
        fprintf(stderr, "Disallow both if and of to be stdin and stdout\n");
        return 1;
    }
    if ((FT_OTHER == rcoll.in_type) && (FT_OTHER == rcoll.out_type) && !gen) {
        fprintf(stderr, "Either 'if' or 'of' must be a sg or raw device\n");
        return 1;
    }
    if (0 == dd_count)
        return 0;
    else if (dd_count < 0) {
        if (FT_SG == rcoll.in_type) {
            res = read_capacity(rcoll.infd, &in_num_sect, &in_sect_sz);
            if (2 == res) {
                fprintf(stderr, "Unit attention, media changed(in), repeat\n");
                res = read_capacity(rcoll.infd, &in_num_sect, &in_sect_sz);
            }
            if (0 != res) {
                fprintf(stderr, "Unable to read capacity on %s\n", inf);
                in_num_sect = -1;
            }
            else {
                if (in_num_sect > skip)
                    in_num_sect -= skip;
            }
        }
        if (FT_SG == rcoll.out_type) {
            res = read_capacity(rcoll.outfd, &out_num_sect, &out_sect_sz);
            if (2 == res) {
                fprintf(stderr, "Unit attention, media changed(out), "
                        "repeat\n");
                res = read_capacity(rcoll.outfd, &out_num_sect, &out_sect_sz);
            }
            if (0 != res) {
                fprintf(stderr, "Unable to read capacity on %s\n", outf);
                out_num_sect = -1;
            }
            else {
                if (out_num_sect > seek)
                    out_num_sect -= seek;
            }
        }
        if (in_num_sect > 0) {
            if (out_num_sect > 0)
                dd_count = (in_num_sect > out_num_sect) ? out_num_sect :
                                                       in_num_sect;
            else
                dd_count = in_num_sect;
        }
        else
            dd_count = out_num_sect;
    }
    if (rcoll.debug > 1)
        fprintf(stderr, "Start of loop, count=%d, in_num_sect=%d, "
                "out_num_sect=%d\n", dd_count, in_num_sect, out_num_sect);
    if (dd_count <= 0) {
        fprintf(stderr, "Couldn't calculate count, please give one\n");
        return 1;
    }

    rcoll.in_count = dd_count;
    rcoll.in_done_count = dd_count;
    rcoll.skip = skip;
    rcoll.in_blk = skip;
    rcoll.out_count = dd_count;
    rcoll.out_done_count = dd_count;
    rcoll.seek = seek;
    rcoll.out_blk = seek;

    if ((FT_SG == rcoll.in_type) || (FT_SG == rcoll.out_type))
        rcoll.num_rq_elems = num_threads;
    else
        rcoll.num_rq_elems = 1;
    if (prepare_rq_elems(&rcoll, inf, outf)) {
        fprintf(stderr, "Setup failure, perhaps no memory\n");
        return 1;
    }

    first_xfer = 1;
    stop_after_write = 0;
    terminate = 0;
    seek_skip =  rcoll.seek - rcoll.skip;
    if (do_time) {
        start_tm.tv_sec = 0;
        start_tm.tv_usec = 0;
        gettimeofday(&start_tm, NULL);
    }
    while (rcoll.out_done_count > 0) { /* >>>>>>>>> main loop */
        req_index = -1;
        qstate = decider(&rcoll, first_xfer, &req_index);
        rep = (req_index < 0) ? NULL : (rcoll.req_arr + req_index);
        switch (qstate) {
        case QS_IDLE:
            if ((NULL == rep) || (rcoll.in_count <= 0)) {
                /* usleep(1000); */
                /* do_poll(&rcoll, 10, NULL); */
                /* do_poll(&rcoll, 0, NULL); */
                break;
            }
            if (rcoll.debug > 8)
                fprintf(stderr, "    sgq_dd: non-sleeping QS_IDLE state, "
                                "req_index=%d\n", req_index);
            if (first_xfer >= 2)
                first_xfer = 0;
            else if (1 == first_xfer)
                ++first_xfer;
            if (stop_after_write) {
                terminate = 1;
                break;
            }
            blocks = (rcoll.in_count > rcoll.bpt) ? rcoll.bpt : rcoll.in_count;
            rep->wr = 0;
            rep->blk = rcoll.in_blk;
            rep->num_blks = blocks;
            rcoll.in_blk += blocks;
            rcoll.in_count -= blocks;

            if (FT_SG == rcoll.in_type) {
                res = sg_start_io(rep);
                if (0 != res) {
                    if (1 == res)
                        fprintf(stderr, "Out of memory starting sg io\n");
                    terminate = 1;
                }
            }
            else {
                res = normal_in_operation(&rcoll, rep, blocks);
                if (res < 0)
                    terminate = 1;
                else if (res > 0)
                    stop_after_write = 1;
            }
            break;
        case QS_IN_FINISHED:
            if (rcoll.debug > 8)
                fprintf(stderr, "    sgq_dd: state is QS_IN_FINISHED, "
                                "req_index=%d\n", req_index);
            if ((rep->blk + seek_skip) != rcoll.out_blk) {
                /* if write would be out of sequence then wait */
                if (rcoll.debug > 4)
                    fprintf(stderr, "    sgq_dd: QS_IN_FINISHED, "
                            "out of sequence\n");
                usleep(200);
                break;
            }
            rep->wr = 1;
            rep->blk = rcoll.out_blk;
            blocks = rep->num_blks;
            rcoll.out_blk += blocks;
            rcoll.out_count -= blocks;

            if (FT_SG == rcoll.out_type) {
                res = sg_start_io(rep);
                if (0 != res) {
                    if (1 == res)
                        fprintf(stderr, "Out of memory starting sg io\n");
                    terminate = 1;
                }
            }
            else {
                if (normal_out_operation(&rcoll, rep, blocks) < 0)
                    terminate = 1;
            }
            break;
        case QS_IN_POLL:
            if (rcoll.debug > 8)
                fprintf(stderr, "    sgq_dd: state is QS_IN_POLL, "
                                "req_index=%d\n", req_index);
            res = sg_fin_in_operation(&rcoll, rep);
            if (res < 0)
                terminate = 1;
            else if (res > 1) {
                if (first_xfer) {
                    /* only retry on first xfer */
                    if (0 != sg_start_io(rep))
                        terminate = 1;
                }
                else
                    terminate = 1;
            }
            break;
        case QS_OUT_POLL:
            if (rcoll.debug > 8)
                fprintf(stderr, "    sgq_dd: state is QS_OUT_POLL, "
                                "req_index=%d\n", req_index);
            res = sg_fin_out_operation(&rcoll, rep);
            if (res < 0)
                terminate = 1;
            else if (res > 1) {
                if (first_xfer) {
                    /* only retry on first xfer */
                    if (0 != sg_start_io(rep))
                        terminate = 1;
                }
                else
                    terminate = 1;
            }
            break;
        default:
            if (rcoll.debug > 8)
                fprintf(stderr, "    sgq_dd: state is ?????\n");
            terminate = 1;
            break;
        }
        if (terminate)
            break;
    } /* >>>>>>>>>>>>> end of main loop */

    if ((do_time) && (start_tm.tv_sec || start_tm.tv_usec)) {
        struct timeval res_tm;
        double a, b;

        gettimeofday(&end_tm, NULL);
        res_tm.tv_sec = end_tm.tv_sec - start_tm.tv_sec;
        res_tm.tv_usec = end_tm.tv_usec - start_tm.tv_usec;
        if (res_tm.tv_usec < 0) {
            --res_tm.tv_sec;
            res_tm.tv_usec += 1000000;
        }
        a = res_tm.tv_sec;
        a += (0.000001 * res_tm.tv_usec);
        b = (double)rcoll.bs * (dd_count - rcoll.out_done_count);
        printf("time to transfer data was %d.%06d secs",
               (int)res_tm.tv_sec, (int)res_tm.tv_usec);
        if ((a > 0.00001) && (b > 511))
            printf(", %.2f MB/sec\n", b / (a * 1000000.0));
        else
            printf("\n");
    }

    if (STDIN_FILENO != rcoll.infd)
        close(rcoll.infd);
    if (STDOUT_FILENO != rcoll.outfd)
        close(rcoll.outfd);
    res = 0;
    if (0 != rcoll.out_count) {
        fprintf(stderr, ">>>> Some error occurred,\n");
        res = 2;
    }
    print_stats();
    if (rcoll.dio_incomplete) {
        int fd;
        char c;

        fprintf(stderr, ">> Direct IO requested but incomplete %d times\n",
                rcoll.dio_incomplete);
        if ((fd = open(sg_allow_dio, O_RDONLY)) >= 0) {
            if (1 == read(fd, &c, 1)) {
                if ('0' == c)
                    fprintf(stderr, ">>> %s set to '0' but should be set "
                            "to '1' for direct IO\n", sg_allow_dio);
            }
            close(fd);
        }
    }
    if (rcoll.sum_of_resids)
        fprintf(stderr, ">> Non-zero sum of residual counts=%d\n",
               rcoll.sum_of_resids);
    return res;
}