string.zig

pub fn strcpy(dest: [*:0]u8, src: [*:0]const u8) [*:0]u8 {
    var d = dest;
    var s = src;
    while (s[0] != 0) {
        d[0] = s[0];
        d += 1;
        s += 1;
    }
    d[0] = 0;
    return dest;
}

pub fn strcat(dest: [*:0]u8, src: [*:0]const u8) [*:0]u8 {
    var d = dest;
    while (d[0] != 0) d += 1;
    var s = src;
    while (s[0] != 0) {
        d[0] = s[0];
        d += 1;
        s += 1;
    }
    d[0] = 0;
    return dest;
}

pub fn strcmp(cs: [*:0]const u8, ct: [*:0]const u8) i32 {
    var i: usize = 0;
    while (cs[i] == ct[i] and cs[i] != 0) i += 1;
    return @as(i32, cs[i]) - @as(i32, ct[i]);
}

pub fn strlen(s: [*:0]const u8) usize {
    var i: usize = 0;
    while (s[i] != 0) i += 1;
    return i;
}

pub fn memcpy(dest: ?*anyopaque, src: ?*const anyopaque, n: i32) ?*anyopaque {
    asm volatile ("cld; rep; movsb"
        :
        : [src] "{S}" (src),
          [dest] "{D}" (dest),
          [n] "{c}" (n),
        : "memory"
    );
    return dest;
}

pub fn memmove(dest: ?*anyopaque, src: ?*const anyopaque, n: i32) ?*anyopaque {
    asm volatile ("cld; rep; movsb"
        :
        : [src] "{S}" (src),
          [dest] "{D}" (dest),
          [n] "{c}" (n),
        : "memory"
    );
    return dest;
}

pub fn memchr(cs: ?*const anyopaque, c: u8, count: i32) ?*anyopaque {
    var s = @as([*]const u8, @ptrCast(cs));
    var i: i32 = 0;
    while (i < count) {
        if (s[i] == c) return @as(*anyopaque, @constCast(@as(*const anyopaque, @ptrCast(&s[i]))));
        i += 1;
    }
    return null;
}