source: vbox/trunk/src/libs/liblzma-5.4.1/common/vli_encoder.c

///////////////////////////////////////////////////////////////////////////////
//
/// \file       vli_encoder.c
/// \brief      Encodes variable-length integers
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "common.h"


extern LZMA_API(lzma_ret)
lzma_vli_encode(lzma_vli vli, size_t *vli_pos,
                uint8_t *restrict out, size_t *restrict out_pos,
                size_t out_size)
{
        // If we haven't been given vli_pos, work in single-call mode.
        size_t vli_pos_internal = 0;
        if (vli_pos == NULL) {
                vli_pos = &vli_pos_internal;

                // In single-call mode, we expect that the caller has
                // reserved enough output space.
                if (*out_pos >= out_size)
                        return LZMA_PROG_ERROR;
        } else {
                // This never happens when we are called by liblzma, but
                // may happen if called directly from an application.
                if (*out_pos >= out_size)
                        return LZMA_BUF_ERROR;
        }

        // Validate the arguments.
        if (*vli_pos >= LZMA_VLI_BYTES_MAX || vli > LZMA_VLI_MAX)
                return LZMA_PROG_ERROR;

        // Shift vli so that the next bits to encode are the lowest. In
        // single-call mode this never changes vli since *vli_pos is zero.
        vli >>= *vli_pos * 7;

        // Write the non-last bytes in a loop.
        while (vli >= 0x80) {
                // We don't need *vli_pos during this function call anymore,
                // but update it here so that it is ready if we need to
                // return before the whole integer has been decoded.
                ++*vli_pos;
                assert(*vli_pos < LZMA_VLI_BYTES_MAX);

                // Write the next byte.
                out[*out_pos] = (uint8_t)(vli) | 0x80;
                vli >>= 7;

                if (++*out_pos == out_size)
                        return vli_pos == &vli_pos_internal
                                        ? LZMA_PROG_ERROR : LZMA_OK;
        }

        // Write the last byte.
        out[*out_pos] = (uint8_t)(vli);
        ++*out_pos;
        ++*vli_pos;

        return vli_pos == &vli_pos_internal ? LZMA_OK : LZMA_STREAM_END;

}