duktape-1.5.2/src-separate/duk_util_bitencoder.c

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/*
 *  Bitstream encoder.
 */
 
#include "duk_internal.h"
 
DUK_INTERNAL void duk_be_encode(duk_bitencoder_ctx *ctx, duk_uint32_t data, duk_small_int_t bits) {
    duk_uint8_t tmp;
 
    DUK_ASSERT(ctx != NULL);
    DUK_ASSERT(ctx->currbits < 8);
 
    /* This limitation would be fixable but adds unnecessary complexity. */
    DUK_ASSERT(bits >= 1 && bits <= 24);
 
    ctx->currval = (ctx->currval << bits) | data;
    ctx->currbits += bits;
 
    while (ctx->currbits >= 8) {
        if (ctx->offset < ctx->length) {
            tmp = (duk_uint8_t) ((ctx->currval >> (ctx->currbits - 8)) & 0xff);
            ctx->data[ctx->offset++] = tmp;
        } else {
            /* If buffer has been exhausted, truncate bitstream */
            ctx->truncated = 1;
        }
 
        ctx->currbits -= 8;
    }
}
 
DUK_INTERNAL void duk_be_finish(duk_bitencoder_ctx *ctx) {
    duk_small_int_t npad;
 
    DUK_ASSERT(ctx != NULL);
    DUK_ASSERT(ctx->currbits < 8);
 
    npad = (duk_small_int_t) (8 - ctx->currbits);
    if (npad > 0) {
        duk_be_encode(ctx, 0, npad);
    }
    DUK_ASSERT(ctx->currbits == 0);
}