--- /dev/null
+/* zran.c -- example of deflate stream indexing and random access
+ * Copyright (C) 2005, 2012, 2018, 2023 Mark Adler
+ * For conditions of distribution and use, see copyright notice in zlib.h
+ * Version 1.4 13 Apr 2023 Mark Adler */
+
+/* Version History:
+ 1.0 29 May 2005 First version
+ 1.1 29 Sep 2012 Fix memory reallocation error
+ 1.2 14 Oct 2018 Handle gzip streams with multiple members
+ Add a header file to facilitate usage in applications
+ 1.3 18 Feb 2023 Permit raw deflate streams as well as zlib and gzip
+ Permit crossing gzip member boundaries when extracting
+ Support a size_t size when extracting (was an int)
+ Do a binary search over the index for an access point
+ Expose the access point type to enable save and load
+ 1.4 13 Apr 2023 Add a NOPRIME define to not use inflatePrime()
+ */
+
+// Illustrate the use of Z_BLOCK, inflatePrime(), and inflateSetDictionary()
+// for random access of a compressed file. A file containing a raw deflate
+// stream is provided on the command line. The compressed stream is decoded in
+// its entirety, and an index built with access points about every SPAN bytes
+// in the uncompressed output. The compressed file is left open, and can then
+// be read randomly, having to decompress on the average SPAN/2 uncompressed
+// bytes before getting to the desired block of data.
+//
+// An access point can be created at the start of any deflate block, by saving
+// the starting file offset and bit of that block, and the 32K bytes of
+// uncompressed data that precede that block. Also the uncompressed offset of
+// that block is saved to provide a reference for locating a desired starting
+// point in the uncompressed stream. deflate_index_build() decompresses the
+// input raw deflate stream a block at a time, and at the end of each block
+// decides if enough uncompressed data has gone by to justify the creation of a
+// new access point. If so, that point is saved in a data structure that grows
+// as needed to accommodate the points.
+//
+// To use the index, an offset in the uncompressed data is provided, for which
+// the latest access point at or preceding that offset is located in the index.
+// The input file is positioned to the specified location in the index, and if
+// necessary the first few bits of the compressed data is read from the file.
+// inflate is initialized with those bits and the 32K of uncompressed data, and
+// decompression then proceeds until the desired offset in the file is reached.
+// Then decompression continues to read the requested uncompressed data from
+// the file.
+//
+// There is some fair bit of overhead to starting inflation for the random
+// access, mainly copying the 32K byte dictionary. If small pieces of the file
+// are being accessed, it would make sense to implement a cache to hold some
+// lookahead to avoid many calls to deflate_index_extract() for small lengths.
+//
+// Another way to build an index would be to use inflateCopy(). That would not
+// be constrained to have access points at block boundaries, but would require
+// more memory per access point, and could not be saved to a file due to the
+// use of pointers in the state. The approach here allows for storage of the
+// index in a file.
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <limits.h>
+#include "zlib.h"
+#include "zran.h"
+
+#define WINSIZE 32768U // sliding window size
+#define CHUNK 16384 // file input buffer size
+
+// See comments in zran.h.
+void deflate_index_free(struct deflate_index *index) {
+ if (index != NULL) {
+ free(index->list);
+ free(index);
+ }
+}
+
+// Add an access point to the list. If out of memory, deallocate the existing
+// list and return NULL. index->mode is temporarily the allocated number of
+// access points, until it is time for deflate_index_build() to return. Then
+// index->mode is set to the mode of inflation.
+static struct deflate_index *add_point(struct deflate_index *index, int bits,
+ off_t in, off_t out, unsigned left,
+ unsigned char *window) {
+ if (index == NULL) {
+ // The list is empty. Create it, starting with eight access points.
+ index = malloc(sizeof(struct deflate_index));
+ if (index == NULL)
+ return NULL;
+ index->have = 0;
+ index->mode = 8;
+ index->list = malloc(sizeof(point_t) * index->mode);
+ if (index->list == NULL) {
+ free(index);
+ return NULL;
+ }
+ }
+
+ else if (index->have == index->mode) {
+ // The list is full. Make it bigger.
+ index->mode <<= 1;
+ point_t *next = realloc(index->list, sizeof(point_t) * index->mode);
+ if (next == NULL) {
+ deflate_index_free(index);
+ return NULL;
+ }
+ index->list = next;
+ }
+
+ // Fill in the access point and increment how many we have.
+ point_t *next = (point_t *)(index->list) + index->have++;
+ if (index->have < 0) {
+ // Overflowed the int!
+ deflate_index_free(index);
+ return NULL;
+ }
+ next->out = out;
+ next->in = in;
+ next->bits = bits;
+ if (left)
+ memcpy(next->window, window + WINSIZE - left, left);
+ if (left < WINSIZE)
+ memcpy(next->window + left, window, WINSIZE - left);
+
+ // Return the index, which may have been newly allocated or destroyed.
+ return index;
+}
+
+// Decompression modes. These are the inflateInit2() windowBits parameter.
+#define RAW -15
+#define ZLIB 15
+#define GZIP 31
+
+// See comments in zran.h.
+int deflate_index_build(FILE *in, off_t span, struct deflate_index **built) {
+ // Set up inflation state.
+ z_stream strm = {0}; // inflate engine (gets fired up later)
+ unsigned char buf[CHUNK]; // input buffer
+ unsigned char win[WINSIZE] = {0}; // output sliding window
+ off_t totin = 0; // total bytes read from input
+ off_t totout = 0; // total bytes uncompressed
+ int mode = 0; // mode: RAW, ZLIB, or GZIP (0 => not set yet)
+
+ // Decompress from in, generating access points along the way.
+ int ret; // the return value from zlib, or Z_ERRNO
+ off_t last; // last access point uncompressed offset
+ struct deflate_index *index = NULL; // list of access points
+ do {
+ // Assure available input, at least until reaching EOF.
+ if (strm.avail_in == 0) {
+ strm.avail_in = fread(buf, 1, sizeof(buf), in);
+ totin += strm.avail_in;
+ strm.next_in = buf;
+ if (strm.avail_in < sizeof(buf) && ferror(in)) {
+ ret = Z_ERRNO;
+ break;
+ }
+
+ if (mode == 0) {
+ // At the start of the input -- determine the type. Assume raw
+ // if it is neither zlib nor gzip. This could in theory result
+ // in a false positive for zlib, but in practice the fill bits
+ // after a stored block are always zeros, so a raw stream won't
+ // start with an 8 in the low nybble.
+ mode = strm.avail_in == 0 ? RAW : // empty -- will fail
+ (strm.next_in[0] & 0xf) == 8 ? ZLIB :
+ strm.next_in[0] == 0x1f ? GZIP :
+ /* else */ RAW;
+ ret = inflateInit2(&strm, mode);
+ if (ret != Z_OK)
+ break;
+ }
+ }
+
+ // Assure available output. This rotates the output through, for use as
+ // a sliding window on the uncompressed data.
+ if (strm.avail_out == 0) {
+ strm.avail_out = sizeof(win);
+ strm.next_out = win;
+ }
+
+ if (mode == RAW && index == NULL)
+ // We skip the inflate() call at the start of raw deflate data in
+ // order generate an access point there. Set data_type to imitate
+ // the end of a header.
+ strm.data_type = 0x80;
+ else {
+ // Inflate and update the number of uncompressed bytes.
+ unsigned before = strm.avail_out;
+ ret = inflate(&strm, Z_BLOCK);
+ totout += before - strm.avail_out;
+ }
+
+ if ((strm.data_type & 0xc0) == 0x80 &&
+ (index == NULL || totout - last >= span)) {
+ // We are at the end of a header or a non-last deflate block, so we
+ // can add an access point here. Furthermore, we are either at the
+ // very start for the first access point, or there has been span or
+ // more uncompressed bytes since the last access point, so we want
+ // to add an access point here.
+ index = add_point(index, strm.data_type & 7, totin - strm.avail_in,
+ totout, strm.avail_out, win);
+ if (index == NULL) {
+ ret = Z_MEM_ERROR;
+ break;
+ }
+ last = totout;
+ }
+
+ if (ret == Z_STREAM_END && mode == GZIP &&
+ (strm.avail_in || ungetc(getc(in), in) != EOF))
+ // There is more input after the end of a gzip member. Reset the
+ // inflate state to read another gzip member. On success, this will
+ // set ret to Z_OK to continue decompressing.
+ ret = inflateReset2(&strm, GZIP);
+
+ // Keep going until Z_STREAM_END or error. If the compressed data ends
+ // prematurely without a file read error, Z_BUF_ERROR is returned.
+ } while (ret == Z_OK);
+ inflateEnd(&strm);
+
+ if (ret != Z_STREAM_END) {
+ // An error was encountered. Discard the index and return a negative
+ // error code.
+ deflate_index_free(index);
+ return ret == Z_NEED_DICT ? Z_DATA_ERROR : ret;
+ }
+
+ // Shrink the index to only the occupied access points and return it.
+ index->mode = mode;
+ index->length = totout;
+ point_t *list = realloc(index->list, sizeof(point_t) * index->have);
+ if (list == NULL) {
+ // Seems like a realloc() to make something smaller should always work,
+ // but just in case.
+ deflate_index_free(index);
+ return Z_MEM_ERROR;
+ }
+ index->list = list;
+ *built = index;
+ return index->have;
+}
+
+#ifdef NOPRIME
+// Support zlib versions before 1.2.3 (July 2005), or incomplete zlib clones
+// that do not have inflatePrime().
+
+# define INFLATEPRIME inflatePreface
+
+// Append the low bits bits of value to in[] at bit position *have, updating
+// *have. value must be zero above its low bits bits. bits must be positive.
+// This assumes that any bits above the *have bits in the last byte are zeros.
+// That assumption is preserved on return, as any bits above *have + bits in
+// the last byte written will be set to zeros.
+static inline void append_bits(unsigned value, int bits,
+ unsigned char *in, int *have) {
+ in += *have >> 3; // where the first bits from value will go
+ int k = *have & 7; // the number of bits already there
+ *have += bits;
+ if (k)
+ *in |= value << k; // write value above the low k bits
+ else
+ *in = value;
+ k = 8 - k; // the number of bits just appended
+ while (bits > k) {
+ value >>= k; // drop the bits appended
+ bits -= k;
+ k = 8; // now at a byte boundary
+ *++in = value;
+ }
+}
+
+// Insert enough bits in the form of empty deflate blocks in front of the
+// low bits bits of value, in order to bring the sequence to a byte boundary.
+// Then feed that to inflate(). This does what inflatePrime() does, except that
+// a negative value of bits is not supported. bits must be in 0..16. If the
+// arguments are invalid, Z_STREAM_ERROR is returned. Otherwise the return
+// value from inflate() is returned.
+static int inflatePreface(z_stream *strm, int bits, int value) {
+ // Check input.
+ if (strm == Z_NULL || bits < 0 || bits > 16)
+ return Z_STREAM_ERROR;
+ if (bits == 0)
+ return Z_OK;
+ value &= (2 << (bits - 1)) - 1;
+
+ // An empty dynamic block with an odd number of bits (95). The high bit of
+ // the last byte is unused.
+ static const unsigned char dyn[] = {
+ 4, 0xe0, 0x81, 8, 0, 0, 0, 0, 0x20, 0xa8, 0xab, 0x1f
+ };
+ const int dynlen = 95; // number of bits in the block
+
+ // Build an input buffer for inflate that is a multiple of eight bits in
+ // length, and that ends with the low bits bits of value.
+ unsigned char in[(dynlen + 3 * 10 + 16 + 7) / 8];
+ int have = 0;
+ if (bits & 1) {
+ // Insert an empty dynamic block to get to an odd number of bits, so
+ // when bits bits from value are appended, we are at an even number of
+ // bits.
+ memcpy(in, dyn, sizeof(dyn));
+ have = dynlen;
+ }
+ while ((have + bits) & 7)
+ // Insert empty fixed blocks until appending bits bits would put us on
+ // a byte boundary. This will insert at most three fixed blocks.
+ append_bits(2, 10, in, &have);
+
+ // Append the bits bits from value, which takes us to a byte boundary.
+ append_bits(value, bits, in, &have);
+
+ // Deliver the input to inflate(). There is no output space provided, but
+ // inflate() can't get stuck waiting on output not ingesting all of the
+ // provided input. The reason is that there will be at most 16 bits of
+ // input from value after the empty deflate blocks (which themselves
+ // generate no output). At least ten bits are needed to generate the first
+ // output byte from a fixed block. The last two bytes of the buffer have to
+ // be ingested in order to get ten bits, which is the most that value can
+ // occupy.
+ strm->avail_in = have >> 3;
+ strm->next_in = in;
+ strm->avail_out = 0;
+ strm->next_out = in; // not used, but can't be NULL
+ return inflate(strm, Z_NO_FLUSH);
+}
+
+#else
+# define INFLATEPRIME inflatePrime
+#endif
+
+// See comments in zran.h.
+ptrdiff_t deflate_index_extract(FILE *in, struct deflate_index *index,
+ off_t offset, unsigned char *buf, size_t len) {
+ // Do a quick sanity check on the index.
+ if (index == NULL || index->have < 1 || index->list[0].out != 0)
+ return Z_STREAM_ERROR;
+
+ // If nothing to extract, return zero bytes extracted.
+ if (len == 0 || offset < 0 || offset >= index->length)
+ return 0;
+
+ // Find the access point closest to but not after offset.
+ int lo = -1, hi = index->have;
+ point_t *point = index->list;
+ while (hi - lo > 1) {
+ int mid = (lo + hi) >> 1;
+ if (offset < point[mid].out)
+ hi = mid;
+ else
+ lo = mid;
+ }
+ point += lo;
+
+ // Initialize the input file and prime the inflate engine to start there.
+ int ret = fseeko(in, point->in - (point->bits ? 1 : 0), SEEK_SET);
+ if (ret == -1)
+ return Z_ERRNO;
+ int ch = 0;
+ if (point->bits && (ch = getc(in)) == EOF)
+ return ferror(in) ? Z_ERRNO : Z_BUF_ERROR;
+ z_stream strm = {0};
+ ret = inflateInit2(&strm, RAW);
+ if (ret != Z_OK)
+ return ret;
+ if (point->bits)
+ INFLATEPRIME(&strm, point->bits, ch >> (8 - point->bits));
+ inflateSetDictionary(&strm, point->window, WINSIZE);
+
+ // Skip uncompressed bytes until offset reached, then satisfy request.
+ unsigned char input[CHUNK];
+ unsigned char discard[WINSIZE];
+ offset -= point->out; // number of bytes to skip to get to offset
+ size_t left = len; // number of bytes left to read after offset
+ do {
+ if (offset) {
+ // Discard up to offset uncompressed bytes.
+ strm.avail_out = offset < WINSIZE ? (unsigned)offset : WINSIZE;
+ strm.next_out = discard;
+ }
+ else {
+ // Uncompress up to left bytes into buf.
+ strm.avail_out = left < UINT_MAX ? (unsigned)left : UINT_MAX;
+ strm.next_out = buf + len - left;
+ }
+
+ // Uncompress, setting got to the number of bytes uncompressed.
+ if (strm.avail_in == 0) {
+ // Assure available input.
+ strm.avail_in = fread(input, 1, CHUNK, in);
+ if (strm.avail_in < CHUNK && ferror(in)) {
+ ret = Z_ERRNO;
+ break;
+ }
+ strm.next_in = input;
+ }
+ unsigned got = strm.avail_out;
+ ret = inflate(&strm, Z_NO_FLUSH);
+ got -= strm.avail_out;
+
+ // Update the appropriate count.
+ if (offset)
+ offset -= got;
+ else
+ left -= got;
+
+ // If we're at the end of a gzip member and there's more to read,
+ // continue to the next gzip member.
+ if (ret == Z_STREAM_END && index->mode == GZIP) {
+ // Discard the gzip trailer.
+ unsigned drop = 8; // length of gzip trailer
+ if (strm.avail_in >= drop) {
+ strm.avail_in -= drop;
+ strm.next_in += drop;
+ }
+ else {
+ // Read and discard the remainder of the gzip trailer.
+ drop -= strm.avail_in;
+ strm.avail_in = 0;
+ do {
+ if (getc(in) == EOF)
+ // The input does not have a complete trailer.
+ return ferror(in) ? Z_ERRNO : Z_BUF_ERROR;
+ } while (--drop);
+ }
+
+ if (strm.avail_in || ungetc(getc(in), in) != EOF) {
+ // There's more after the gzip trailer. Use inflate to skip the
+ // gzip header and resume the raw inflate there.
+ inflateReset2(&strm, GZIP);
+ do {
+ if (strm.avail_in == 0) {
+ strm.avail_in = fread(input, 1, CHUNK, in);
+ if (strm.avail_in < CHUNK && ferror(in)) {
+ ret = Z_ERRNO;
+ break;
+ }
+ strm.next_in = input;
+ }
+ strm.avail_out = WINSIZE;
+ strm.next_out = discard;
+ ret = inflate(&strm, Z_BLOCK); // stop at end of header
+ } while (ret == Z_OK && (strm.data_type & 0x80) == 0);
+ if (ret != Z_OK)
+ break;
+ inflateReset2(&strm, RAW);
+ }
+ }
+
+ // Continue until we have the requested data, the deflate data has
+ // ended, or an error is encountered.
+ } while (ret == Z_OK && left);
+ inflateEnd(&strm);
+
+ // Return the number of uncompressed bytes read into buf, or the error.
+ return ret == Z_OK || ret == Z_STREAM_END ? len - left : ret;
+}
+
+#ifdef TEST
+
+#define SPAN 1048576L // desired distance between access points
+#define LEN 16384 // number of bytes to extract
+
+// Demonstrate the use of deflate_index_build() and deflate_index_extract() by
+// processing the file provided on the command line, and extracting LEN bytes
+// from 2/3rds of the way through the uncompressed output, writing that to
+// stdout. An offset can be provided as the second argument, in which case the
+// data is extracted from there instead.
+int main(int argc, char **argv) {
+ // Open the input file.
+ if (argc < 2 || argc > 3) {
+ fprintf(stderr, "usage: zran file.raw [offset]\n");
+ return 1;
+ }
+ FILE *in = fopen(argv[1], "rb");
+ if (in == NULL) {
+ fprintf(stderr, "zran: could not open %s for reading\n", argv[1]);
+ return 1;
+ }
+
+ // Get optional offset.
+ off_t offset = -1;
+ if (argc == 3) {
+ char *end;
+ offset = strtoll(argv[2], &end, 10);
+ if (*end || offset < 0) {
+ fprintf(stderr, "zran: %s is not a valid offset\n", argv[2]);
+ return 1;
+ }
+ }
+
+ // Build index.
+ struct deflate_index *index = NULL;
+ int len = deflate_index_build(in, SPAN, &index);
+ if (len < 0) {
+ fclose(in);
+ switch (len) {
+ case Z_MEM_ERROR:
+ fprintf(stderr, "zran: out of memory\n");
+ break;
+ case Z_BUF_ERROR:
+ fprintf(stderr, "zran: %s ended prematurely\n", argv[1]);
+ break;
+ case Z_DATA_ERROR:
+ fprintf(stderr, "zran: compressed data error in %s\n", argv[1]);
+ break;
+ case Z_ERRNO:
+ fprintf(stderr, "zran: read error on %s\n", argv[1]);
+ break;
+ default:
+ fprintf(stderr, "zran: error %d while building index\n", len);
+ }
+ return 1;
+ }
+ fprintf(stderr, "zran: built index with %d access points\n", len);
+
+ // Use index by reading some bytes from an arbitrary offset.
+ unsigned char buf[LEN];
+ if (offset == -1)
+ offset = ((index->length + 1) << 1) / 3;
+ ptrdiff_t got = deflate_index_extract(in, index, offset, buf, LEN);
+ if (got < 0)
+ fprintf(stderr, "zran: extraction failed: %s error\n",
+ got == Z_MEM_ERROR ? "out of memory" : "input corrupted");
+ else {
+ fwrite(buf, 1, got, stdout);
+ fprintf(stderr, "zran: extracted %ld bytes at %lld\n", got, offset);
+ }
+
+ // Clean up and exit.
+ deflate_index_free(index);
+ fclose(in);
+ return 0;
+}
+
+#endif
notaz.gp2x.de / pcsx_rearmed.git / blobdiff