get_angle.inc.c

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/*
 * The angle of (x, y), 0x100 a turn, from the stage's table of tangents
 * angleTangents
 */
s32 getAngle(s32 x, s32 y) {
    s32 result = 0;
    s32 ratio = 0;
    s32 base;
    s32 i;
 
    if (x <= 0 && y >= 0) {
        base = 0;
    } else if (x >= 0 && y >= 0) {
        base = 0x40;
    } else if (x >= 0 && y <= 0) {
        base = 0x80;
    } else if (x <= 0 && y <= 0) {
        base = 0xC0;
    } else {
        base = 0;
    }
    if (x < 0) {
        x = -x;
    }
    if (y < 0) {
        y = -y;
    }
    if (x == y) {
        return base | 0x20;
    }
    if (y < x) {
        ratio = y * 0xFFFF / x;
    } else if (x < y) {
        ratio = x * 0xFFFF / y;
    }
    for (i = 0; i <= 0x20; i++) {
        if (angleTangents[i] <= ratio && ratio <= angleTangents[i + 1]) {
            switch (base) {
            case 0:
            case 0x80:
                if (y < x) {
                    result = i;
                } else if (x < y) {
                    result = 0x40 - i;
                }
                return result + base;
            case 0x40:
            case 0xC0:
                if (y < x) {
                    result = 0x40 - i;
                } else if (x < y) {
                    result = i;
                }
                return result + base;
            }
        }
    }
    return 0xFF;
}