eBookReaderSwitch/mupdf/source/fitz/compress.c

#include "mupdf/fitz.h"

#include <zlib.h>

#include <limits.h>

/*
	Compress source_length bytes of data starting
	at source, into a buffer of length *destLen, starting at dest.
	*compressed_length will be updated on exit to contain the size
	actually used.
 */
void fz_deflate(fz_context *ctx, unsigned char *dest, size_t *destLen, const unsigned char *source, size_t sourceLen, fz_deflate_level level)
{
	z_stream stream;
	int err;
	size_t left;

	left = *destLen;
	*destLen = 0;

	stream.zalloc = fz_zlib_alloc;
	stream.zfree = fz_zlib_free;
	stream.opaque = ctx;

	err = deflateInit(&stream, (int)level);
	if (err != Z_OK)
		fz_throw(ctx, FZ_ERROR_GENERIC, "zlib compression failed: %d", err);

	stream.next_out = dest;
	stream.avail_out = 0;
	stream.next_in = (z_const Bytef *)source;
	stream.avail_in = 0;

	do {
		if (stream.avail_out == 0) {
			stream.avail_out = left > UINT_MAX ? UINT_MAX : (uInt)left;
			left -= stream.avail_out;
		}
		if (stream.avail_in == 0) {
			stream.avail_in = sourceLen > UINT_MAX ? UINT_MAX : (uInt)sourceLen;
			sourceLen -= stream.avail_in;
		}
		err = deflate(&stream, sourceLen ? Z_NO_FLUSH : Z_FINISH);
	} while (err == Z_OK);

	/* We might have problems if the compressed length > uLong sized. Tough, for now. */
	*destLen = stream.total_out;
	deflateEnd(&stream);
	if (err != Z_STREAM_END)
		fz_throw(ctx, FZ_ERROR_GENERIC, "Zlib failure: %d", err);
}

/*
	Compress source_length bytes of data starting
	at source, into a new memory block malloced for that purpose.
	*compressed_length is updated on exit to contain the size used.
	Ownership of the block is returned from this function, and the
	caller is therefore responsible for freeing it. The block may be
	considerably larger than is actually required. The caller is
	free to fz_realloc it down if it wants to.
*/
unsigned char *fz_new_deflated_data(fz_context *ctx, size_t *compressed_length, const unsigned char *source, size_t source_length, fz_deflate_level level)
{
	size_t bound = fz_deflate_bound(ctx, source_length);
	unsigned char *cdata = Memento_label(fz_malloc(ctx, bound), "deflated_data");
	*compressed_length = 0;

	fz_try(ctx)
		fz_deflate(ctx, cdata, &bound, source, source_length, level);
	fz_catch(ctx)
	{
		fz_free(ctx, cdata);
		fz_rethrow(ctx);
	}

	*compressed_length = bound;
	return cdata;
}

/*
	Compress the contents of a fz_buffer into a
	new block malloced for that purpose. *compressed_length is updated
	on exit to contain the size used. Ownership of the block is
	returned from this function, and the caller is therefore responsible
	for freeing it. The block may be considerably larger than is
	actually required. The caller is free to fz_realloc it down if it
	wants to.
*/
unsigned char *fz_new_deflated_data_from_buffer(fz_context *ctx, size_t *compressed_length, fz_buffer *buffer, fz_deflate_level level)
{
	unsigned char *data;
	size_t size = fz_buffer_storage(ctx, buffer, &data);

	if (size == 0 || data == NULL)
	{
		*compressed_length = 0;
		return NULL;
	}

	return fz_new_deflated_data(ctx, compressed_length, data, size, level);
}

/*
	Returns the upper bound on the
	size of flated data of length size.
 */
size_t fz_deflate_bound(fz_context *ctx, size_t size)
{
	/* Copied from zlib to account for size_t vs uLong */
	return size + (size >> 12) + (size >> 14) + (size >> 25) + 13;
}