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/*
* Copyright (c) 2018 Stefan Sperling <stsp@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
struct got_delta {
STAILQ_ENTRY(got_delta) entry;
off_t offset;
size_t tslen;
int type;
size_t size;
off_t data_offset;
};
struct got_delta_chain {
int nentries;
STAILQ_HEAD(, got_delta) entries;
};
#define GOT_DELTA_CHAIN_RECURSION_MAX 500
struct got_delta *got_delta_open(off_t, size_t, int, size_t, off_t);
const struct got_error *got_delta_chain_get_base_type(int *,
struct got_delta_chain *);
const struct got_error *got_delta_get_sizes(uint64_t *, uint64_t *,
const uint8_t *, size_t);
const struct got_error *got_delta_apply_in_mem(uint8_t *, size_t,
const uint8_t *, size_t, uint8_t *, size_t *, size_t);
const struct got_error *got_delta_apply(FILE *, const uint8_t *, size_t,
FILE *, size_t *);
/*
* The amount of result data we may keep in RAM while applying deltas.
* Data larger than this is written to disk during delta application (slow).
*/
#define GOT_DELTA_RESULT_SIZE_CACHED_MAX (8 * 1024 * 1024) /* bytes */
/*
* Definitions for delta data streams.
*/
#define GOT_DELTA_STREAM_LENGTH_MIN 4 /* bytes */
/*
* A delta stream begins with two size fields. The first specifies the
* size of the delta base, and the second describes the expected size of
* the data which results from applying the delta to the delta base.
*
* Each size field uses a variable length encoding:
* size0...sizeN form a 7+7+7+...+7 bit integer, where size0 is the
* least significant part and sizeN is the most significant part.
* If the MSB of a size byte is set, an additional size byte follows.
*/
#define GOT_DELTA_SIZE_VAL_MASK 0x7f
#define GOT_DELTA_SIZE_SHIFT 7
#define GOT_DELTA_SIZE_MORE 0x80
/*
* The rest of the delta stream contains copy instructions.
*
* A base copy instruction copies N bytes starting at offset X from the delta
* base to the output. Base copy instructions begin with a byte which has its
* MSB set. The remaining bits of this byte describe how many offset and
* length value bytes follow.
* The offset X is encoded in 1 to 4 bytes, and the length N is encoded in
* 1 to 3 bytes. For both values, the first byte contributes the least
* significant part and the last byte which is present contributes the
* most significant part.
* If the offset value is omitted, an offset of zero is implied.
* If the length value is omitted, a default length of 65536 bytes is implied.
*
* An inline copy instruction copies data from the delta stream to the output.
* Such instructions begin with one byte which does not have the MSB set
* and which specifies the length of the inline data which follows (i.e.
* at most 127 bytes). A length value of zero is invalid.
*/
#define GOT_DELTA_BASE_COPY 0x80
#define GOT_DELTA_COPY_OFF1 0x01 /* byte 1 of offset is present */
#define GOT_DELTA_COPY_OFF2 0x02 /* byte 2 of offset is present */
#define GOT_DELTA_COPY_OFF3 0x04 /* byte 3 of offset is present */
#define GOT_DELTA_COPY_OFF4 0x08 /* byte 4 of offset is present */
#define GOT_DELTA_COPY_LEN1 0x10 /* byte 1 of length is present */
#define GOT_DELTA_COPY_LEN2 0x20 /* byte 2 of length is present */
#define GOT_DELTA_COPY_LEN3 0x40 /* byte 3 of length is present */
#define GOT_DELTA_COPY_DEFAULT_OFF 0x0 /* default offset if omitted */
#define GOT_DELTA_COPY_DEFAULT_LEN 0x10000 /* default length if omitted */
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