1// SPDX-License-Identifier: 0BSD
2
3///////////////////////////////////////////////////////////////////////////////
4//
5/// \file       vli_encoder.c
6/// \brief      Encodes variable-length integers
7//
8//  Author:     Lasse Collin
9//
10///////////////////////////////////////////////////////////////////////////////
11
12#include "common.h"
13
14
15extern LZMA_API(lzma_ret)
16lzma_vli_encode(lzma_vli vli, size_t *vli_pos,
17		uint8_t *restrict out, size_t *restrict out_pos,
18		size_t out_size)
19{
20	// If we haven't been given vli_pos, work in single-call mode.
21	size_t vli_pos_internal = 0;
22	if (vli_pos == NULL) {
23		vli_pos = &vli_pos_internal;
24
25		// In single-call mode, we expect that the caller has
26		// reserved enough output space.
27		if (*out_pos >= out_size)
28			return LZMA_PROG_ERROR;
29	} else {
30		// This never happens when we are called by liblzma, but
31		// may happen if called directly from an application.
32		if (*out_pos >= out_size)
33			return LZMA_BUF_ERROR;
34	}
35
36	// Validate the arguments.
37	if (*vli_pos >= LZMA_VLI_BYTES_MAX || vli > LZMA_VLI_MAX)
38		return LZMA_PROG_ERROR;
39
40	// Shift vli so that the next bits to encode are the lowest. In
41	// single-call mode this never changes vli since *vli_pos is zero.
42	vli >>= *vli_pos * 7;
43
44	// Write the non-last bytes in a loop.
45	while (vli >= 0x80) {
46		// We don't need *vli_pos during this function call anymore,
47		// but update it here so that it is ready if we need to
48		// return before the whole integer has been decoded.
49		++*vli_pos;
50		assert(*vli_pos < LZMA_VLI_BYTES_MAX);
51
52		// Write the next byte.
53		out[*out_pos] = (uint8_t)(vli) | 0x80;
54		vli >>= 7;
55
56		if (++*out_pos == out_size)
57			return vli_pos == &vli_pos_internal
58					? LZMA_PROG_ERROR : LZMA_OK;
59	}
60
61	// Write the last byte.
62	out[*out_pos] = (uint8_t)(vli);
63	++*out_pos;
64	++*vli_pos;
65
66	return vli_pos == &vli_pos_internal ? LZMA_OK : LZMA_STREAM_END;
67
68}
69