pcompress/main.c

/*
 * This file is a part of Pcompress, a chunked parallel multi-
 * algorithm lossless compression and decompression program.
 *
 * Copyright (C) 2012 Moinak Ghosh. All rights reserved.
 * Use is subject to license terms.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * moinakg@belenix.org, http://moinakg.wordpress.com/
 * 
 * This program includes partly-modified public domain/LGPL source
 * code from the LZMA SDK: http://www.7-zip.org/sdk.html
 */

/*
 * pcompress - Do a chunked parallel compression/decompression of a file.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <strings.h>
#include <limits.h>
#include <unistd.h>
#include <byteswap.h>
#include <libgen.h>
#include <utils.h>
#include <pcompress.h>
#include <allocator.h>

/* Needed for CLzmaEncprops. */
#include <LzmaEnc.h>

/*
 * We use 5MB chunks by default.
 */
#define	DEFAULT_CHUNKSIZE	(5 * 1024 * 1024)

struct wdata {
	struct cmp_data **dary;
	int wfd;
	int nprocs;
};


static void * writer_thread(void *dat);
static int init_algo(const char *algo, int bail);

static compress_func_ptr _compress_func;
static compress_func_ptr _decompress_func;
static init_func_ptr _init_func;
static deinit_func_ptr _deinit_func;
static int main_cancel;
static int adapt_mode = 0;
static int pipe_mode = 0;
static int nthreads = 0;
static int hide_stats = 1;
static unsigned int chunk_num;
static const char *exec_name;
static const char *algo = NULL;

static void
usage(void)
{
	fprintf(stderr,
	    "Usage:\n"
	    "1) To compress a file:\n"
	    "   %s -c <algorithm> [-l <compress level>] [-s <chunk size>] <file>\n"
	    "   Where <algorithm> can be the folowing:\n"
	    "   zlib   - The base Zlib format compression (not Gzip).\n"
	    "   lzma   - The LZMA (Lempel-Ziv Markov) algorithm from 7Zip.\n"
	    "   bzip2  - Bzip2 Algorithm from libbzip2.\n"
	    "   ppmd   - The PPMd algorithm excellent for textual data. PPMd requires\n"
	    "            at least 64MB X CPUs more memory than the other modes.\n"
	    "   adapt  - Adaptive mode where lzma or bzip2 will be used per chunk,\n"
	    "            depending on which one produces better compression. This mode\n"
	    "            is obviously fairly slow and requires double the memory of\n"
	    "            standalone bzip2 or lzma modes.\n"
	    "   adapt2 - Adaptive mode which includes lzma, bzip2 and ppmd. This requires\n"
	    "            even more memory than adapt mode, is more slower and potentially\n"
	    "            produces the best compression.\n"
	    "   <chunk_size> - This can be in bytes or can use the following suffixes:\n"
	    "            g - Gigabyte, m - Megabyte, k - Kilobyte.\n"
	    "            Larger chunks produce better compression at the cost of memory.\n"
	    "   <compress_level> - Can be a number from 0 meaning minimum and 14 meaning\n"
	    "            maximum compression.\n\n"
	    "2) To decompress a file compressed using above command:\n"
	    "   %s -d <compressed file> <target file>\n"
	    "3) To operate as a pipe, read from stdin and write to stdout:\n"
	    "   %s <-c ...|-d ...> -p\n"
	    "4) Number of threads can optionally be specified: -t <1 - 256 count>\n"
	    "5) Pass '-M' to display memory allocator statistics\n\n",
	    exec_name, exec_name, exec_name);
}

/*
 * This routine is called in multiple threads. Calls the decompression handler
 * as encoded in the file header. For adaptive mode the handler adapt_decompress()
 * in turns looks at the chunk header and call the actualy decompression
 * routine.
 */
static void *
perform_decompress(void *dat)
{
	struct cmp_data *tdat = (struct cmp_data *)dat;
	ssize_t _chunksize;
	int type, rv;
	typeof (tdat->crc64) crc64;
	uchar_t HDR;
	uchar_t *cseg;

redo:
	sem_wait(&tdat->start_sem);
	if (unlikely(tdat->cancel)) {
		tdat->len_cmp = 0;
		sem_post(&tdat->cmp_done_sem);
		return (0);
	}

	/*
	 * If the last read returned a 0 quit.
	 */
	if (tdat->rbytes == 0) {
		tdat->len_cmp = 0;
		tdat->crc64 = 0;
		goto cont;
	}

	cseg = tdat->compressed_chunk + sizeof (crc64);
	_chunksize = tdat->chunksize;
	tdat->crc64 = htonll(*((typeof (crc64) *)(tdat->compressed_chunk)));
	HDR = *cseg;
	if (HDR & CHSIZE_MASK) {
		uchar_t *rseg;

		tdat->rbytes -= sizeof (ssize_t);
		tdat->len_cmp -= sizeof (ssize_t);
		rseg = tdat->compressed_chunk + tdat->rbytes;
		_chunksize = ntohll(*((ssize_t *)rseg));
	}
	if (HDR & COMPRESSED) {
		rv = tdat->decompress(cseg, tdat->len_cmp, tdat->uncompressed_chunk,
		    &_chunksize, tdat->level, tdat->data);
	} else {
		memcpy(cseg + CHDR_SZ, tdat->uncompressed_chunk, _chunksize);
	}
	tdat->len_cmp = _chunksize;

	if (rv == -1) {
		tdat->len_cmp = 0;
		fprintf(stderr, "ERROR: Chunk %d, decompression failed.\n", tdat->id);
		goto cont;
	}
	/*
	 * Re-compute checksum of original uncompressed chunk.
	 * If it does not match we set length of chunk to 0 to indicate
	 * exit to the writer thread.
	 */
	crc64 = lzma_crc64(tdat->uncompressed_chunk, _chunksize, 0);
	if (crc64 != tdat->crc64) {
		tdat->len_cmp = 0;
		fprintf(stderr, "ERROR: Chunk %d, checksums do not match.\n", tdat->id);
	}

cont:
	sem_post(&tdat->cmp_done_sem);
	goto redo;
}

/*
 * File decompression routine.
 *
 * Compressed file Format
 * ----------------------
 * File Header:
 * Algorithm string:  8 bytes.
 * Version number:    4 bytes.
 * Chunk size:        8 bytes.
 * Compression Level: 4 bytes;
 *
 * Chunk Header:
 * Compressed length: 8 bytes.
 * CRC64 Checksum:    8 bytes.
 * Chunk flags:       1 byte.
 * 
 * Chunk Flags, 8 bits:
 * I  I  I  I  I  I  I  I
 * |     |  |           |
 * |     |  |           `- 0 - Uncompressed
 * |     |  |              1 - Compressed
 * |     |  |
 * |     |  `------------- 1 - Bzip2 (Adaptive Mode)
 * |     `---------------- 1 - Lzma (Adaptive Mode)
 * |
 * `---------------------- 1 - Last Chunk flag
 *
 * A file trailer to indicate end.
 * Zero Compressed length: 8 zero bytes.
 */
#define UNCOMP_BAIL err = 1; goto uncomp_done

static void
start_decompress(const char *filename, const char *to_filename)
{
	char tmpfile[MAXPATHLEN];
	char algorithm[ALGO_SZ];
	struct stat sbuf;
	struct wdata w;
	int compfd = -1, i, p;
	int uncompfd = -1, err, np, bail;
	int version, nprocs, thread = 0, level;
	ssize_t chunksize, compressed_chunksize;
	struct cmp_data **dary, *tdat;
	pthread_t writer_thr;

	err = 0;
	/*
	 * Open files and do sanity checks.
	 */
	if (!pipe_mode) {
		if ((compfd = open(filename, O_RDONLY, 0)) == -1)
			err_exit(1, "Cannot open: %s", filename);

		if (fstat(compfd, &sbuf) == -1)
			err_exit(1, "Cannot stat: %s", filename);
		if (sbuf.st_size == 0)
			return;

		if ((uncompfd = open(to_filename, O_WRONLY|O_CREAT|O_TRUNC, 0)) == -1) {
			close(compfd);
			err_exit(1, "Cannot open: %s", to_filename);
		}
	} else {
		compfd = fileno(stdin);
		if (compfd == -1) {
			perror("fileno ");
			UNCOMP_BAIL;
		}
		uncompfd = fileno(stdout);
		if (uncompfd == -1) {
			perror("fileno ");
			UNCOMP_BAIL;
		}
	}

	/*
	 * Read file header pieces and verify.
	 */
	if (Read(compfd, algorithm, ALGO_SZ) < ALGO_SZ) {
		perror("Read: ");
		UNCOMP_BAIL;
	}
	if (init_algo(algorithm, 0) != 0) {
		fprintf(stderr, "%s is not a pcompressed file.\n", filename);
		UNCOMP_BAIL;
	}

	if (Read(compfd, &version, sizeof (version)) < sizeof (version) ||
	    Read(compfd, &chunksize, sizeof (chunksize)) < sizeof (chunksize) ||
	    Read(compfd, &level, sizeof (level)) < sizeof (level)) {
		perror("Read: ");
		UNCOMP_BAIL;
	}

	version = ntohl(version);
	chunksize = ntohll(chunksize);
	level = ntohl(level);

	if (version != 1) {
		fprintf(stderr, "Unsupported version: %d\n", version);
		err = 1;
		goto uncomp_done;
	}

	compressed_chunksize = chunksize + (chunksize >> 6) + sizeof (uint64_t)
	    + sizeof (chunksize);

	if (nthreads == 0)
		nprocs = sysconf(_SC_NPROCESSORS_ONLN);
	else
		nprocs = nthreads;

	fprintf(stderr, "Scaling to %d threads\n", nprocs);
	dary = (struct cmp_data **)slab_alloc(NULL, sizeof (struct cmp_data *) * nprocs);
	for (i = 0; i < nprocs; i++) {
		dary[i] = (struct cmp_data *)slab_alloc(NULL, sizeof (struct cmp_data));
		if (!dary[i]) {
			fprintf(stderr, "Out of memory\n");
			UNCOMP_BAIL;
		}
		tdat = dary[i];
		tdat->compressed_chunk = (uchar_t *)slab_alloc(NULL,
		    compressed_chunksize + CHDR_SZ);
		if (!tdat->compressed_chunk) {
			fprintf(stderr, "Out of memory\n");
			UNCOMP_BAIL;
		}
		tdat->uncompressed_chunk = (uchar_t *)slab_alloc(NULL, chunksize);
		if (!tdat->uncompressed_chunk) {
			fprintf(stderr, "Out of memory\n");
			UNCOMP_BAIL;
		}
		tdat->cmp_seg = tdat->uncompressed_chunk;
		tdat->chunksize = chunksize;
		tdat->compress = _compress_func;
		tdat->decompress = _decompress_func;
		tdat->cancel = 0;
		tdat->level = level;
		sem_init(&(tdat->start_sem), 0, 0);
		sem_init(&(tdat->cmp_done_sem), 0, 0);
		sem_init(&(tdat->write_done_sem), 0, 1);
		if (_init_func)
			_init_func(&(tdat->data), &(tdat->level), chunksize);
		if (pthread_create(&(tdat->thr), NULL, perform_decompress,
		    (void *)tdat) != 0) {
			perror("Error in thread creation: ");
			UNCOMP_BAIL;
		}
	}
	thread = 1;

	w.dary = dary;
	w.wfd = uncompfd;
	w.nprocs = nprocs;
	if (pthread_create(&writer_thr, NULL, writer_thread, (void *)(&w)) != 0) {
		perror("Error in thread creation: ");
		UNCOMP_BAIL;
	}

	/*
	 * Now read from the compressed file in variable compressed chunk size.
	 * First the size is read from the chunk header and then as many bytes +
	 * CRC64 checksum size are read and passed to decompression thread.
	 * Chunk sequencing is ensured.
	 */
	chunk_num = 0;
	np = 0;
	bail = 0;
	while (!bail) {
		ssize_t rb;

		if (main_cancel) break;
		for (p = 0; p < nprocs; p++) {
			np = p;
			tdat = dary[p];
			sem_wait(&tdat->write_done_sem);
			if (main_cancel) break;
			tdat->id = chunk_num;

			/*
			 * First read length of compressed chunk.
			 */
			rb = Read(compfd, &tdat->len_cmp, sizeof (tdat->len_cmp));
			if (rb != sizeof (tdat->len_cmp)) {
				if (rb < 0) perror("Read: ");
				else
					fprintf(stderr, "Incomplete chunk %d header,"
					    "file corrupt\n", chunk_num);
				UNCOMP_BAIL;
			}
			tdat->len_cmp = htonll(tdat->len_cmp);
			/*
			 * Zero compressed len means end of file.
			 */
			if (tdat->len_cmp == 0) {
				bail = 1;
				break;
			}

			/*
			 * Now read compressed chunk including the crc64 checksum.
			 */
			tdat->rbytes = Read(compfd, tdat->compressed_chunk,
			    tdat->len_cmp + sizeof(tdat->crc64) + CHDR_SZ);

			if (main_cancel) break;
			if (tdat->rbytes < tdat->len_cmp + sizeof(tdat->crc64) + CHDR_SZ) {
				if (tdat->rbytes < 0) {
					perror("Read: ");
					UNCOMP_BAIL;
				} else {
					fprintf(stderr, "Incomplete chunk %d, file corrupt.\n",
					    chunk_num);
					UNCOMP_BAIL;
				}
			}
			sem_post(&tdat->start_sem);
			chunk_num++;
		}
	}


	if (!main_cancel) {
		for (p = 0; p < nprocs; p++) {
			if (p == np) continue;
			tdat = dary[p];
			sem_wait(&tdat->write_done_sem);
		}
		thread = 0;
	}
uncomp_done:
	if (thread) {
		for (i = 0; i < nprocs; i++) {
			tdat = dary[i];
			tdat->cancel = 1;
			tdat->len_cmp = 0;
			sem_post(&tdat->start_sem);
			sem_post(&tdat->cmp_done_sem);
			pthread_join(tdat->thr, NULL);
		}
		pthread_join(writer_thr, NULL);
	}

	/*
	 * Ownership and mode of target should be same as original.
	 */
	fchmod(uncompfd, sbuf.st_mode);
	if (fchown(uncompfd, sbuf.st_uid, sbuf.st_gid) == -1)
		perror("Chown ");
	if (dary != NULL) {
		for (i = 0; i < nprocs; i++) {
			slab_free(NULL, dary[i]->uncompressed_chunk);
			slab_free(NULL, dary[i]->compressed_chunk);
			if (_deinit_func)
				_deinit_func(&(tdat->data));
			slab_free(NULL, dary[i]);
		}
		slab_free(NULL, dary);
	}
	if (!pipe_mode) {
		if (compfd != -1) close(compfd);
		if (uncompfd != -1) close(uncompfd);
	}

	slab_cleanup(hide_stats);
}

static void *
perform_compress(void *dat) {
	struct cmp_data *tdat = (struct cmp_data *)dat;
	typeof (tdat->chunksize) _chunksize, len_cmp;
	int type, rv;

redo:
	sem_wait(&tdat->start_sem);
	if (unlikely(tdat->cancel)) {
		tdat->len_cmp = 0;
		sem_post(&tdat->cmp_done_sem);
		return (0);
	}

	/*
	 * Compute checksum of original uncompressed chunk.
	 */
	tdat->crc64 = lzma_crc64(tdat->uncompressed_chunk, tdat->rbytes, 0);

	_chunksize = tdat->rbytes;
	rv = tdat->compress(tdat->uncompressed_chunk, tdat->rbytes,
	    tdat->compressed_chunk + CHDR_SZ, &_chunksize, tdat->level,
	    tdat->data);

	/*
	 * Sanity check to ensure compressed data is lesser than original.
	 * If at all compression expands/does not shrink data then the chunk
	 * will be left uncompressed. Also if the compression errored the
	 * chunk will be left uncompressed.
	 */
	tdat->len_cmp = _chunksize;
	if (_chunksize >= tdat->chunksize || rv < 0) {
		memcpy(tdat->compressed_chunk + CHDR_SZ, tdat->uncompressed_chunk,
		    tdat->rbytes);
		type = UNCOMPRESSED;
		tdat->len_cmp = tdat->rbytes;
	} else {
		type = COMPRESSED;
	}

	/*
	 * Insert compressed chunk length and CRC64 checksum into
	 * chunk header.
	 */
	len_cmp = tdat->len_cmp;
	*((typeof (len_cmp) *)(tdat->cmp_seg)) = htonll(tdat->len_cmp);
	*((typeof (tdat->crc64) *)(tdat->cmp_seg + sizeof (tdat->crc64))) = htonll(tdat->crc64);
	tdat->len_cmp += CHDR_SZ;
	tdat->len_cmp += sizeof (len_cmp);
	tdat->len_cmp += sizeof (tdat->crc64);

	if (adapt_mode)
		type |= (rv << 4);

	/*
	 * If last chunk is less than chunksize, store this length as well.
	 */
	if (tdat->rbytes < tdat->chunksize) {
		type |= CHSIZE_MASK;
		*((typeof (tdat->rbytes) *)(tdat->cmp_seg + tdat->len_cmp)) = htonll(tdat->rbytes);
		tdat->len_cmp += sizeof (tdat->rbytes);
		len_cmp += sizeof (tdat->rbytes);
		*((typeof (len_cmp) *)(tdat->cmp_seg)) = htonll(len_cmp);
	}
	/*
	 * Set the chunk header flags.
	 */
	*(tdat->compressed_chunk) = type;

cont:
	sem_post(&tdat->cmp_done_sem);
	goto redo;
}

static void *
writer_thread(void *dat) {
	int p;
	struct wdata *w = (struct wdata *)dat;
	struct cmp_data *tdat;
	ssize_t wbytes;

repeat:
	for (p = 0; p < w->nprocs; p++) {
		tdat = w->dary[p];
		sem_wait(&tdat->cmp_done_sem);
		if (tdat->len_cmp == 0) {
			goto do_cancel;
		}

		wbytes = Write(w->wfd, tdat->cmp_seg, tdat->len_cmp);
		if (unlikely(wbytes != tdat->len_cmp)) {
			int i;

			perror("Chunk Write: ");
do_cancel:
			main_cancel = 1;
			for (i = 0; i < w->nprocs; i++) {
				tdat->cancel = 1;
				sem_post(&tdat->start_sem);
				sem_post(&tdat->write_done_sem);
			}
			return (0);
		}
		sem_post(&tdat->write_done_sem);
	}
	goto repeat;
}

/*
 * File compression routine. Can use as many threads as there are
 * logical cores unless user specified something different. There is
 * not much to gain from nthreads > n logical cores however.
 */
#define COMP_BAIL err = 1; goto comp_done

static void
start_compress(const char *filename, uint64_t chunksize, int level)
{
	struct wdata w;
	char tmpfile[MAXPATHLEN];
	char to_filename[MAXPATHLEN];
	ssize_t compressed_chunksize;
	ssize_t n_chunksize, rbytes;
	int version;
	struct stat sbuf;
	int compfd = -1, uncompfd = -1, err;
	int i, thread = 0, bail;
	int nprocs, np, p;
	struct cmp_data **dary = NULL, *tdat;
	pthread_t writer_thr;
	uchar_t *cread_buf, *pos;

	/*
	 * Compressed buffer size must include zlib scratch space and
	 * chunk header space.
	 * See http://www.zlib.net/manual.html#compress2
	 * 
	 * We do this unconditionally whether user mentioned zlib or not
	 * to keep it simple. While zlib scratch space is only needed at
	 * runtime, chunk header is stored in the file.
	 *
	 * See start_decompress() routine for details of chunk header.
	 * We also keep extra 8-byte space for the last chunk's size.
	 */
	compressed_chunksize = chunksize + (chunksize >> 6) +
	    sizeof (chunksize) + sizeof (uint64_t) + sizeof (chunksize);
	err = 0;

	/* A host of sanity checks. */
	if (!pipe_mode) {
		if ((uncompfd = open(filename, O_RDWR, 0)) == -1)
			err_exit(1, "Cannot open: %s", filename);

		if (fstat(uncompfd, &sbuf) == -1) {
			close(uncompfd);
			err_exit(1, "Cannot stat: %s", filename);
		}

		if (!S_ISREG(sbuf.st_mode)) {
			close(uncompfd);
			err_exit(0, "File %s is not a regular file.\n", filename);
		}

		if (sbuf.st_size == 0) {
			close(uncompfd);
			return;
		}

		/*
		 * Adjust chunk size for small files. We then get an archive with
		 * a single chunk for the entire file.
		 */
		if (sbuf.st_size < chunksize) {
			chunksize = sbuf.st_size;
		}

		/*
		 * Create a temporary file to hold compressed data which is renamed at
		 * the end. The target file name is same as original file with the '.pz'
		 * extension appended.
		 */
		strcpy(tmpfile, filename);
		strcpy(tmpfile, dirname(tmpfile));
		strcat(tmpfile, "/.pcompXXXXXX");
		snprintf(to_filename, sizeof (to_filename), "%s" COMP_EXTN, filename);
		if ((compfd = mkstemp(tmpfile)) == -1) {
			perror("mkstemp ");
			COMP_BAIL;
		}
	} else {
		/*
		 * Use stdin/stdout for pipe mode.
		 */
		compfd = fileno(stdout);
		if (compfd == -1) {
			perror("fileno ");
			COMP_BAIL;
		}
		uncompfd = fileno(stdin);
		if (uncompfd == -1) {
			perror("fileno ");
			COMP_BAIL;
		}
	}

	if (nthreads == 0)
		nprocs = sysconf(_SC_NPROCESSORS_ONLN);
	else
		nprocs = nthreads;

	fprintf(stderr, "Scaling to %d threads\n", nprocs);
	slab_cache_add(chunksize);
	slab_cache_add(compressed_chunksize + CHDR_SZ);
	slab_cache_add(sizeof (struct cmp_data));

	dary = (struct cmp_data **)slab_alloc(NULL, sizeof (struct cmp_data *) * nprocs);
	cread_buf = (uchar_t *)slab_alloc(NULL, chunksize);
	if (!cread_buf) {
		fprintf(stderr, "Out of memory\n");
		COMP_BAIL;
	}

	for (i = 0; i < nprocs; i++) {
		dary[i] = (struct cmp_data *)slab_alloc(NULL, sizeof (struct cmp_data));
		if (!dary[i]) {
			fprintf(stderr, "Out of memory\n");
			COMP_BAIL;
		}
		tdat = dary[i];
		tdat->cmp_seg = (uchar_t *)slab_alloc(NULL, compressed_chunksize + CHDR_SZ);
		tdat->compressed_chunk = tdat->cmp_seg + sizeof (chunksize) + sizeof (uint64_t);
		if (!tdat->compressed_chunk) {
			fprintf(stderr, "Out of memory\n");
			COMP_BAIL;
		}
		tdat->uncompressed_chunk = (uchar_t *)slab_alloc(NULL, chunksize);
		if (!tdat->uncompressed_chunk) {
			fprintf(stderr, "Out of memory\n");
			COMP_BAIL;
		}
		tdat->chunksize = chunksize;
		tdat->compress = _compress_func;
		tdat->decompress = _decompress_func;
		tdat->cancel = 0;
		tdat->level = level;
		sem_init(&(tdat->start_sem), 0, 0);
		sem_init(&(tdat->cmp_done_sem), 0, 0);
		sem_init(&(tdat->write_done_sem), 0, 1);
		if (_init_func)
			_init_func(&(tdat->data), &(tdat->level), chunksize);

		if (pthread_create(&(tdat->thr), NULL, perform_compress,
		    (void *)tdat) != 0) {
			perror("Error in thread creation: ");
			COMP_BAIL;
		}
	}
	thread = 1;

	w.dary = dary;
	w.wfd = compfd;
	w.nprocs = nprocs;
	if (pthread_create(&writer_thr, NULL, writer_thread, (void *)(&w)) != 0) {
		perror("Error in thread creation: ");
		COMP_BAIL;
	}

	/*
	 * Write out file header. First insert hdr elements into mem buffer
	 * then write out the full hdr in one shot.
	 */
	memset(cread_buf, 0, ALGO_SZ);
	strncpy(cread_buf, algo, ALGO_SZ);
	version = htonl(VERSION);
	n_chunksize = htonll(chunksize);
	level = htonl(level);
	pos = cread_buf + ALGO_SZ;
	memcpy(pos, &version, sizeof (version));
	pos += sizeof (version);
	memcpy(pos, &n_chunksize, sizeof (n_chunksize));
	pos += sizeof (n_chunksize);
	memcpy(pos, &level, sizeof (level));
	pos += sizeof (level);
	if (Write(compfd, cread_buf, pos - cread_buf) != pos - cread_buf) {
		perror("Write ");
		COMP_BAIL;
	}

	/*
	 * Now read from the uncompressed file in 'chunksize' sized chunks, independently
	 * compress each chunk and write it out. Chunk sequencing is ensured.
	 */
	chunk_num = 0;
	np = 0;
	bail = 0;

	/*
	 * Read the first chunk into a spare buffer (a simple double-buffering).
	 */
	rbytes = Read(uncompfd, cread_buf, chunksize);
	while (!bail) {
		uchar_t *tmp;

		if (main_cancel) break;
		for (p = 0; p < nprocs; p++) {
			np = p;
			tdat = dary[p];
			if (main_cancel) break;
			/* Wait for previous chunk compression to complete. */
			sem_wait(&tdat->write_done_sem);
			if (main_cancel) break;

			/*
			 * Once previous chunk is done swap already read buffer and
			 * it's size into the thread data.
			 */
			tdat->id = chunk_num;
			tmp = tdat->uncompressed_chunk;
			tdat->uncompressed_chunk = cread_buf;
			cread_buf = tmp;
			tdat->rbytes = rbytes;
			if (rbytes < chunksize) {
				bail = 1;
				if (rbytes < 0) {
					perror("Read: ");
					COMP_BAIL;

				} else if (tdat->rbytes == 0) { /* EOF */
					break;
				}
				np = nprocs + 1;
				sem_post(&tdat->start_sem);
				break;
			}
			/* Signal the compression thread to start */
			sem_post(&tdat->start_sem);
			/*
			 * Read the next buffer we want to process while previous
			 * buffer is in progress.
			 */
			rbytes = Read(uncompfd, cread_buf, chunksize);
			chunk_num++;
		}
	}

	if (!main_cancel) {
		/* Wait for all remaining chunks to finish. */
		for (p = 0; p < nprocs; p++) {
			if (p == np) continue;
			tdat = dary[p];
			sem_wait(&tdat->write_done_sem);
		}
	} else {
		err = 1;
	}

comp_done:
	if (thread) {
		for (i = 0; i < nprocs; i++) {
			tdat = dary[i];
			tdat->cancel = 1;
			tdat->len_cmp = 0;
			sem_post(&tdat->start_sem);
			sem_post(&tdat->cmp_done_sem);
			pthread_join(tdat->thr, NULL);
		}
		pthread_join(writer_thr, NULL);
	}

	if (err) {
		if (compfd != -1 && !pipe_mode)
			unlink(tmpfile);
		fprintf(stderr, "Error compressing file: %s\n", filename);
	} else {
		/*
		* Write a trailer of zero chunk length.
		*/
		compressed_chunksize = 0;
		if (Write(compfd, &compressed_chunksize,
		    sizeof (compressed_chunksize)) < 0) {
			perror("Write ");
			err = 1;
		}

		/*
		 * Rename the temporary file to the actual compressed file
		 * unless we are in a pipe.
		 */
		if (!pipe_mode) {
			/*
			 * Ownership and mode of target should be same as original.
			 */
			fchmod(compfd, sbuf.st_mode);
			if (fchown(compfd, sbuf.st_uid, sbuf.st_gid) == -1)
				perror("chown ");

			if (rename(tmpfile, to_filename) == -1) {
				perror("Cannot rename temporary file ");
				unlink(tmpfile);
			}
		}
	}
	if (dary != NULL) {
		for (i = 0; i < nprocs; i++) {
			slab_free(NULL, dary[i]->uncompressed_chunk);
			slab_free(NULL, dary[i]->cmp_seg);
			if (_deinit_func)
				_deinit_func(&(dary[i]->data));
			slab_free(NULL, dary[i]);
		}
		slab_free(NULL, dary);
	}
	slab_free(NULL, cread_buf);
	if (!pipe_mode) {
		if (compfd != -1) close(compfd);
		if (uncompfd != -1) close(uncompfd);
	}

	slab_cleanup(hide_stats);
}

/*
 * Check the algorithm requested and set the callback routine pointers.
 */
static int
init_algo(const char *algo, int bail)
{
	int rv = 1, i;
	char algorithm[8];

	/* Copy given string into known length buffer to avoid memcmp() overruns. */
	strncpy(algorithm, algo, 8);
	if (memcmp(algorithm, "zlib", 4) == 0) {
		_compress_func = zlib_compress;
		_decompress_func = zlib_decompress;
		_init_func = zlib_init;
		_deinit_func = NULL;
		rv = 0;

	} else if (memcmp(algorithm, "lzma", 4) == 0) {
		_compress_func = lzma_compress;
		_decompress_func = lzma_decompress;
		_init_func = lzma_init;
		_deinit_func = lzma_deinit;
		rv = 0;

	} else if (memcmp(algorithm, "bzip2", 5) == 0) {
		_compress_func = bzip2_compress;
		_decompress_func = bzip2_decompress;
		_init_func = bzip2_init;
		_deinit_func = NULL;
		rv = 0;

	} else if (memcmp(algorithm, "ppmd", 4) == 0) {
		_compress_func = ppmd_compress;
		_decompress_func = ppmd_decompress;
		_init_func = ppmd_init;
		_deinit_func = ppmd_deinit;
		rv = 0;

	/* adapt2 and adapt ordering of the checks matters here. */
	} else if (memcmp(algorithm, "adapt2", 6) == 0) {
		_compress_func = adapt_compress;
		_decompress_func = adapt_decompress;
		_init_func = adapt2_init;
		_deinit_func = adapt_deinit;
		adapt_mode = 1;
		rv = 0;

	} else if (memcmp(algorithm, "adapt", 5) == 0) {
		_compress_func = adapt_compress;
		_decompress_func = adapt_decompress;
		_init_func = adapt_init;
		_deinit_func = adapt_deinit;
		adapt_mode = 1;
		rv = 0;
	}

	return (rv);
}

int
main(int argc, char *argv[])
{
	char *filename = NULL;
	char *to_filename = NULL;
	ssize_t chunksize = DEFAULT_CHUNKSIZE;
	int opt, level, num_rem;
	int do_compress = 0;
	int do_uncompress = 0;

	exec_name = get_execname(argv[0]);
	level = 6;
	slab_init();

	while ((opt = getopt(argc, argv, "dc:s:l:pt:M")) != -1) {
		int ovr;

		switch (opt) {
		    case 'd':
			do_uncompress = 1;
			break;

		    case 'c':
			do_compress = 1;
			algo = optarg;
			if (init_algo(algo, 1) != 0) {
				err_exit(1, "Invalid algorithm %s\n", optarg);
			}
			break;

		    case 's':
			ovr = parse_numeric(&chunksize, optarg);
			if (ovr == 1)
				err_exit(0, "Chunk size too large %s", optarg);
			else if (ovr == 2)
				err_exit(0, "Invalid number %s", optarg);

			if (chunksize < MIN_CHUNK) {
				err_exit(0, "Minimum chunk size is %ld\n", MIN_CHUNK);
			}
			break;

		    case 'l':
			level = atoi(optarg);
			if (level < 0 || level > 14)
				err_exit(0, "Compression level should be in range 0 - 14\n");
			break;

		    case 'p':
			pipe_mode = 1;
			break;

		    case 't':
			nthreads = atoi(optarg);
			if (nthreads < 1 || nthreads > 256)
				err_exit(0, "Thread count should be in range 1 - 256\n");
			break;

		    case 'M':
			hide_stats = 0;
			break;

		    case '?':
		    default:
			usage();
			exit(1);
			break;
		}
	}

	if ((do_compress && do_uncompress) || (!do_compress && !do_uncompress)) {
		usage();
		exit(1);
	}

	/*
	 * Remaining mandatory arguments are the filenames.
	 */
	num_rem = argc - optind;
	if (pipe_mode && num_rem > 0 ) {
		fprintf(stderr, "Filename(s) unexpected for pipe mode\n");
		usage();
		exit(1);
	}

	if (num_rem == 0 && !pipe_mode) {
		usage(); /* At least 1 filename needed. */
		exit(1);

	} else if (num_rem == 1) {
		if (do_compress) {
			char apath[MAXPATHLEN];

			if ((filename = realpath(argv[optind], NULL)) == NULL)
				err_exit(1, "%s", argv[optind]);
			/* Check if compressed file exists */
			strcpy(apath, filename);
			strcat(apath, COMP_EXTN);
			if ((to_filename = realpath(apath, NULL)) != NULL) {
				free(filename);
				err_exit(0, "Compressed file %s exists\n", to_filename);
			}
		} else {
			usage();
			exit(1);
		}
	} else if (num_rem == 2) {
		if (do_uncompress) {
			if ((filename = realpath(argv[optind], NULL)) == NULL)
				err_exit(1, "%s", argv[optind]);
			optind++;
			if ((to_filename = realpath(argv[optind], NULL)) != NULL) {
				free(filename);
				free(to_filename);
				err_exit(0, "File %s exists\n", argv[optind]);
			}
			to_filename = argv[optind];
		} else {
			usage();
			exit(1);
		}
	} else {
		usage();
		exit(1);
	}
	main_cancel = 0;

	/*
	 * Start the main routines.
	 */
	if (do_compress)
		start_compress(filename, chunksize, level);
	else if (do_uncompress)
		start_decompress(filename, to_filename);

	free(filename);
	free((void *)exec_name);
	return (0);
}