mulaw.h

#define BIAS (0x84) /* Bias for linear code. */

static int search(int val, short *table, int size)
{
    int i;

    for (i = 0; i < size; i++) {
        if (val <= *table++)
            return (i);
    }
    return (size);
}

static short seg_end[8] = {0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF};

unsigned char linear2ulaw(int pcm_val) /* 2's complement (16-bit range) */
{
    int mask;
    int seg;
    unsigned char uval;

    /* Get the sign and the magnitude of the value. */
    if (pcm_val < 0) {
        pcm_val = BIAS - pcm_val;
        mask = 0x7F;
    } else {
        pcm_val += BIAS;
        mask = 0xFF;
    }

    /* Convert the scaled magnitude to segment number. */
    seg = search(pcm_val, seg_end, 8);

    /*
     * Combine the sign, segment, quantization bits;
     * and complement the code word.
     */
    if (seg >= 8) /* out of range, return maximum value. */
        return (0x7F ^ mask);
    else {
        uval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0xF);
        return (uval ^ mask);
    }
}