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/* gzread.c -- zlib functions for reading gzip files
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* Copyright (C) 2004, 2005, 2010 Mark Adler
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* For conditions of distribution and use, see copyright notice in zlib.h
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local int gz_load OF((gz_statep, unsigned char *, unsigned, unsigned *));
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local int gz_avail OF((gz_statep));
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local int gz_next4 OF((gz_statep, unsigned long *));
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local int gz_head OF((gz_statep));
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local int gz_decomp OF((gz_statep));
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local int gz_make OF((gz_statep));
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local int gz_skip OF((gz_statep, z_off64_t));
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/* Use read() to load a buffer -- return -1 on error, otherwise 0. Read from
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state->fd, and update state->eof, state->err, and state->msg as appropriate.
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This function needs to loop on read(), since read() is not guaranteed to
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read the number of bytes requested, depending on the type of descriptor. */
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local int gz_load(state, buf, len, have)
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ret = read(state->fd, buf + *have, len - *have);
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} while (*have < len);
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gz_error(state, Z_ERRNO, zstrerror());
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/* Load up input buffer and set eof flag if last data loaded -- return -1 on
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error, 0 otherwise. Note that the eof flag is set when the end of the input
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file is reached, even though there may be unused data in the buffer. Once
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that data has been used, no more attempts will be made to read the file.
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gz_avail() assumes that strm->avail_in == 0. */
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local int gz_avail(state)
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z_streamp strm = &(state->strm);
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if (state->err != Z_OK)
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if (state->eof == 0) {
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if (gz_load(state, state->in, state->size,
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(unsigned *)&(strm->avail_in)) == -1)
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strm->next_in = state->in;
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/* Get next byte from input, or -1 if end or error. */
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#define NEXT() ((strm->avail_in == 0 && gz_avail(state) == -1) ? -1 : \
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(strm->avail_in == 0 ? -1 : \
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(strm->avail_in--, *(strm->next_in)++)))
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/* Get a four-byte little-endian integer and return 0 on success and the value
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in *ret. Otherwise -1 is returned and *ret is not modified. */
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local int gz_next4(state, ret)
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z_streamp strm = &(state->strm);
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val += (unsigned)NEXT() << 8;
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val += (unsigned long)NEXT() << 16;
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val += (unsigned long)ch << 24;
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/* Look for gzip header, set up for inflate or copy. state->have must be zero.
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If this is the first time in, allocate required memory. state->how will be
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left unchanged if there is no more input data available, will be set to COPY
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if there is no gzip header and direct copying will be performed, or it will
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be set to GZIP for decompression, and the gzip header will be skipped so
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that the next available input data is the raw deflate stream. If direct
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copying, then leftover input data from the input buffer will be copied to
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the output buffer. In that case, all further file reads will be directly to
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either the output buffer or a user buffer. If decompressing, the inflate
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state and the check value will be initialized. gz_head() will return 0 on
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success or -1 on failure. Failures may include read errors or gzip header
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local int gz_head(state)
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z_streamp strm = &(state->strm);
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/* allocate read buffers and inflate memory */
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if (state->size == 0) {
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/* allocate buffers */
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state->in = malloc(state->want);
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state->out = malloc(state->want << 1);
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if (state->in == NULL || state->out == NULL) {
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if (state->out != NULL)
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if (state->in != NULL)
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gz_error(state, Z_MEM_ERROR, "out of memory");
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state->size = state->want;
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/* allocate inflate memory */
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state->strm.zalloc = Z_NULL;
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state->strm.zfree = Z_NULL;
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state->strm.opaque = Z_NULL;
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state->strm.avail_in = 0;
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state->strm.next_in = Z_NULL;
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if (inflateInit2(&(state->strm), -15) != Z_OK) { /* raw inflate */
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gz_error(state, Z_MEM_ERROR, "out of memory");
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/* get some data in the input buffer */
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if (strm->avail_in == 0) {
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if (gz_avail(state) == -1)
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if (strm->avail_in == 0)
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/* look for the gzip magic header bytes 31 and 139 */
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if (strm->next_in[0] == 31) {
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if (strm->avail_in == 0 && gz_avail(state) == -1)
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if (strm->avail_in && strm->next_in[0] == 139) {
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/* we have a gzip header, woo hoo! */
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/* skip rest of header */
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if (NEXT() != 8) { /* compression method */
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gz_error(state, Z_DATA_ERROR, "unknown compression method");
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if (flags & 0xe0) { /* reserved flag bits */
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gz_error(state, Z_DATA_ERROR, "unknown header flags set");
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NEXT(); /* modification time */
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NEXT(); /* extra flags */
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NEXT(); /* operating system */
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if (flags & 4) { /* extra field */
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len = (unsigned)NEXT();
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len += (unsigned)NEXT() << 8;
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if (flags & 8) /* file name */
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if (flags & 16) /* comment */
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if (flags & 2) { /* header crc */
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/* an unexpected end of file is not checked for here -- it will be
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noticed on the first request for uncompressed data */
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/* set up for decompression */
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strm->adler = crc32(0L, Z_NULL, 0);
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/* not a gzip file -- save first byte (31) and fall to raw i/o */
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/* doing raw i/o, save start of raw data for seeking, copy any leftover
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input to output -- this assumes that the output buffer is larger than
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the input buffer, which also assures space for gzungetc() */
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state->raw = state->pos;
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state->next = state->out;
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if (strm->avail_in) {
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memcpy(state->next + state->have, strm->next_in, strm->avail_in);
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state->have += strm->avail_in;
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/* Decompress from input to the provided next_out and avail_out in the state.
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If the end of the compressed data is reached, then verify the gzip trailer
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check value and length (modulo 2^32). state->have and state->next are set
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to point to the just decompressed data, and the crc is updated. If the
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trailer is verified, state->how is reset to LOOK to look for the next gzip
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stream or raw data, once state->have is depleted. Returns 0 on success, -1
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on failure. Failures may include invalid compressed data or a failed gzip
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trailer verification. */
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local int gz_decomp(state)
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unsigned long crc, len;
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z_streamp strm = &(state->strm);
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/* fill output buffer up to end of deflate stream */
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had = strm->avail_out;
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/* get more input for inflate() */
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if (strm->avail_in == 0 && gz_avail(state) == -1)
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if (strm->avail_in == 0) {
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gz_error(state, Z_DATA_ERROR, "unexpected end of file");
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/* decompress and handle errors */
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ret = inflate(strm, Z_NO_FLUSH);
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if (ret == Z_STREAM_ERROR || ret == Z_NEED_DICT) {
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gz_error(state, Z_STREAM_ERROR,
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"internal error: inflate stream corrupt");
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if (ret == Z_MEM_ERROR) {
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gz_error(state, Z_MEM_ERROR, "out of memory");
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if (ret == Z_DATA_ERROR) { /* deflate stream invalid */
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gz_error(state, Z_DATA_ERROR,
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strm->msg == NULL ? "compressed data error" : strm->msg);
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} while (strm->avail_out && ret != Z_STREAM_END);
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/* update available output and crc check value */
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state->have = had - strm->avail_out;
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state->next = strm->next_out - state->have;
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strm->adler = crc32(strm->adler, state->next, state->have);
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/* check gzip trailer if at end of deflate stream */
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if (ret == Z_STREAM_END) {
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if (gz_next4(state, &crc) == -1 || gz_next4(state, &len) == -1) {
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gz_error(state, Z_DATA_ERROR, "unexpected end of file");
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if (crc != strm->adler) {
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gz_error(state, Z_DATA_ERROR, "incorrect data check");
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if (len != (strm->total_out & 0xffffffffL)) {
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gz_error(state, Z_DATA_ERROR, "incorrect length check");
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state->how = LOOK; /* ready for next stream, once have is 0 (leave
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state->direct unchanged to remember how) */
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/* good decompression */
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/* Make data and put in the output buffer. Assumes that state->have == 0.
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Data is either copied from the input file or decompressed from the input
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file depending on state->how. If state->how is LOOK, then a gzip header is
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looked for (and skipped if found) to determine wither to copy or decompress.
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Returns -1 on error, otherwise 0. gz_make() will leave state->have as COPY
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or GZIP unless the end of the input file has been reached and all data has
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local int gz_make(state)
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z_streamp strm = &(state->strm);
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if (state->how == LOOK) { /* look for gzip header */
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if (gz_head(state) == -1)
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if (state->have) /* got some data from gz_head() */
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if (state->how == COPY) { /* straight copy */
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if (gz_load(state, state->out, state->size << 1, &(state->have)) == -1)
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state->next = state->out;
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else if (state->how == GZIP) { /* decompress */
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strm->avail_out = state->size << 1;
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strm->next_out = state->out;
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if (gz_decomp(state) == -1)
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/* Skip len uncompressed bytes of output. Return -1 on error, 0 on success. */
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local int gz_skip(state, len)
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/* skip over len bytes or reach end-of-file, whichever comes first */
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/* skip over whatever is in output buffer */
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n = GT_OFF(state->have) || (z_off64_t)state->have > len ?
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(unsigned)len : state->have;
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/* output buffer empty -- return if we're at the end of the input */
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else if (state->eof && state->strm.avail_in == 0)
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/* need more data to skip -- load up output buffer */
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/* get more output, looking for header if required */
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if (gz_make(state) == -1)
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/* -- see zlib.h -- */
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int ZEXPORT gzread(file, buf, len)
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/* get internal structure */
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state = (gz_statep)file;
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strm = &(state->strm);
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/* check that we're reading and that there's no error */
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if (state->mode != GZ_READ || state->err != Z_OK)
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/* since an int is returned, make sure len fits in one, otherwise return
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with an error (this avoids the flaw in the interface) */
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gz_error(state, Z_BUF_ERROR, "requested length does not fit in int");
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/* if len is zero, avoid unnecessary operations */
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/* process a skip request */
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if (gz_skip(state, state->skip) == -1)
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/* get len bytes to buf, or less than len if at the end */
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/* first just try copying data from the output buffer */
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n = state->have > len ? len : state->have;
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memcpy(buf, state->next, n);
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/* output buffer empty -- return if we're at the end of the input */
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else if (state->eof && strm->avail_in == 0)
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/* need output data -- for small len or new stream load up our output
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else if (state->how == LOOK || len < (state->size << 1)) {
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/* get more output, looking for header if required */
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if (gz_make(state) == -1)
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continue; /* no progress yet -- go back to memcpy() above */
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/* the copy above assures that we will leave with space in the
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output buffer, allowing at least one gzungetc() to succeed */
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/* large len -- read directly into user buffer */
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else if (state->how == COPY) { /* read directly */
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if (gz_load(state, buf, len, &n) == -1)
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/* large len -- decompress directly into user buffer */
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else { /* state->how == GZIP */
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strm->avail_out = len;
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strm->next_out = buf;
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if (gz_decomp(state) == -1)
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/* update progress */
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buf = (char *)buf + n;
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/* return number of bytes read into user buffer (will fit in int) */
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/* -- see zlib.h -- */
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int ZEXPORT gzgetc(file)
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unsigned char buf[1];
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/* get internal structure */
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state = (gz_statep)file;
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/* check that we're reading and that there's no error */
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if (state->mode != GZ_READ || state->err != Z_OK)
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/* try output buffer (no need to check for skip request) */
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return *(state->next)++;
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/* nothing there -- try gzread() */
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ret = gzread(file, buf, 1);
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return ret < 1 ? -1 : buf[0];
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/* -- see zlib.h -- */
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int ZEXPORT gzungetc(c, file)
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/* get internal structure */
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state = (gz_statep)file;
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/* check that we're reading and that there's no error */
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if (state->mode != GZ_READ || state->err != Z_OK)
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/* process a skip request */
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if (gz_skip(state, state->skip) == -1)
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/* if output buffer empty, put byte at end (allows more pushing) */
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if (state->have == 0) {
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state->next = state->out + (state->size << 1) - 1;
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/* if no room, give up (must have already done a gzungetc()) */
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if (state->have == (state->size << 1)) {
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gz_error(state, Z_BUF_ERROR, "out of room to push characters");
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/* slide output data if needed and insert byte before existing data */
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if (state->next == state->out) {
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unsigned char *src = state->out + state->have;
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unsigned char *dest = state->out + (state->size << 1);
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while (src > state->out)
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/* -- see zlib.h -- */
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char * ZEXPORT gzgets(file, buf, len)
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/* check parameters and get internal structure */
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if (file == NULL || buf == NULL || len < 1)
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state = (gz_statep)file;
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/* check that we're reading and that there's no error */
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if (state->mode != GZ_READ || state->err != Z_OK)
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/* process a skip request */
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if (gz_skip(state, state->skip) == -1)
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/* copy output bytes up to new line or len - 1, whichever comes first --
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append a terminating zero to the string (we don't check for a zero in
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the contents, let the user worry about that) */
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left = (unsigned)len - 1;
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/* assure that something is in the output buffer */
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if (state->have == 0) {
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if (gz_make(state) == -1)
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return NULL; /* error */
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if (state->have == 0) { /* end of file */
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if (buf == str) /* got bupkus */
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break; /* got something -- return it */
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/* look for end-of-line in current output buffer */
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n = state->have > left ? left : state->have;
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eol = memchr(state->next, '\n', n);
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n = (unsigned)(eol - state->next) + 1;
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/* copy through end-of-line, or remainder if not found */
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memcpy(buf, state->next, n);
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} while (left && eol == NULL);
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/* found end-of-line or out of space -- terminate string and return it */
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/* -- see zlib.h -- */
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int ZEXPORT gzdirect(file)
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/* get internal structure */
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state = (gz_statep)file;
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/* check that we're reading */
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if (state->mode != GZ_READ)
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/* if the state is not known, but we can find out, then do so (this is
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mainly for right after a gzopen() or gzdopen()) */
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if (state->how == LOOK && state->have == 0)
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(void)gz_head(state);
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/* return 1 if reading direct, 0 if decompressing a gzip stream */
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return state->direct;
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/* -- see zlib.h -- */
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int ZEXPORT gzclose_r(file)
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/* get internal structure */
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return Z_STREAM_ERROR;
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state = (gz_statep)file;
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/* check that we're reading */
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if (state->mode != GZ_READ)
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return Z_STREAM_ERROR;
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/* free memory and close file */
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inflateEnd(&(state->strm));
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gz_error(state, Z_OK, NULL);
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ret = close(state->fd);
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return ret ? Z_ERRNO : Z_OK;
added
removed
examples/zlibwrap/zlib/gzread.c
