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