bigint: Fast paths for radix code.

core/math/bigint/example.odin

@@ -46,37 +46,35 @@ demo :: proc() {
 	as, bs, cs: string;
 	err:  Error;
 
-	a, err = init(512);
+	a, err = init(4);
 	defer destroy(a);
-	as, err = itoa(a, 10);
+	as, err = itoa(a);
 	fmt.printf("a: %v, err: %v\n\n", as, err);
 	delete(as);
 
-	b, err = init(42);
+	b, err = init(4);
 	defer destroy(b);
-	bs, err = itoa(b, 10);
-	fmt.printf("b: %v, err: %v\n\n", bs, err);
+	bs, err = itoa(b);
+	fmt.printf("b: %s, err: %v\n\n", bs, err);
 	delete(bs);
 
 	c, err = init();
 	defer destroy(c);
-	cs, err = itoa(c, 10);
-	fmt.printf("c: %v\n", cs);
+	cs, err = itoa(c);
+	fmt.printf("b: %s, err: %v\n\n", cs, err);
 	delete(cs);
 
 	fmt.println("=== Add ===");
 	err = sub(c, a, b);
 
 	fmt.printf("Error: %v\n", err);
-	as, err = itoa(a, 10);
-	bs, err = itoa(b, 10);
-	cs, err = itoa(c, 10);
+	as, err = itoa(a);
+	bs, err = itoa(b);
+	cs, err = itoa(c);
 	fmt.printf("a: %v, bits: %v\n", as, count_bits(a));
 	fmt.printf("b: %v, bits: %v\n", bs, count_bits(b));
 	fmt.printf("c: %v, bits: %v\n", cs, count_bits(c));
 	delete(as); delete(bs); delete(cs);
-
-	fmt.println("radix_size:", radix_size(a, 10));
 }
 
 main :: proc() {

core/math/bigint/log.odin

@@ -11,7 +11,7 @@ package bigint
 
 import "core:fmt"
 
-log_n_int :: proc(a: ^Int, base: int) -> (log: int, err: Error) {
+log_n_int :: proc(a: ^Int, base: DIGIT) -> (log: int, err: Error) {
 	assert_initialized(a);
 	if is_neg(a) || is_zero(a) || base < 2 || DIGIT(base) > _DIGIT_MAX {
 		return -1, .Invalid_Input;
@@ -20,7 +20,7 @@ log_n_int :: proc(a: ^Int, base: int) -> (log: int, err: Error) {
 	/*
 		Fast path for bases that are a power of two.
 	*/
-	if is_power_of_two(base) {
+	if is_power_of_two(int(base)) {
 		return _log_power_of_two(a, base), .OK;
 	}
 
@@ -44,7 +44,7 @@ log_n :: proc{log_n_int, log_n_digit};
 	Returns the log2 of an `Int`, provided `base` is a power of two.
 	Don't call it if it isn't.
 */
-_log_power_of_two :: proc(a: ^Int, base: int) -> (log: int) {
+_log_power_of_two :: proc(a: ^Int, base: DIGIT) -> (log: int) {
 	base := base;
 	y: int;
 	for y = 0; base & 1 == 0; {

core/math/bigint/radix.odin

@@ -15,23 +15,60 @@ import "core:mem"
 import "core:intrinsics"
 import "core:fmt"
 import "core:strings"
+import "core:slice"
 
-itoa :: proc(a: ^Int, radix: int, allocator := context.allocator) -> (res: string, err: Error) {
+/*
+	This version of `itoa` allocates one behalf of the caller. The caller must free the string.
+*/
+itoa_string :: proc(a: ^Int, radix := i8(-1), zero_terminate := false, allocator := context.allocator) -> (res: string, err: Error) {
 	assert_initialized(a);
+	/*
+		Radix defaults to 10.
+	*/
+	radix := radix if radix > 0 else 10;
 
-	if radix < 2 || radix > 64 {
-		return strings.clone("", allocator), .Invalid_Input;
+	/*
+		TODO: If we want to write a prefix for some of the radixes, we can oversize the buffer.
+		Then after the digits are written and the string is reversed
+	*/
+
+	/*
+		Calculate the size of the buffer we need.
+	*/
+	size: int;
+	size, err = radix_size(a, radix);
+	if zero_terminate {
+		size += 1;
 	}
 
 	/*
-		Fast path for radixes that are a power of two.
+		Exit if calculating the size returned an error.
 	*/
-	if is_power_of_two(radix) {
-
+	if err != .OK {
+		if zero_terminate {
+			return string(cstring("")), err;
+		}
+		return "", err;
 	}
 
+	/*
+		Allocate the buffer we need.
+	*/
+	buffer := make([]u8, size);
 
+	/*
+		Write the digits out into the buffer.
+	*/
+	written: int;
+	written, err = itoa_raw(a, radix, buffer, zero_terminate);
 
+	/*
+		For now, delete the buffer and fall back to the below on failure.
+	*/
+	if err == .OK {
+		return string(buffer[:written]), .OK;
+	}
+	delete(buffer);
 
 	fallback :: proc(a: ^Int, print_raw := false) -> string {
 		   if print_raw {
@@ -48,12 +85,91 @@ itoa :: proc(a: ^Int, radix: int, allocator := context.allocator) -> (res: strin
 	return strings.clone(fallback(a), allocator), .Unimplemented;
 }
 
-int_to_string :: itoa;
+/*
+	This version of `itoa` allocates one behalf of the caller. The caller must free the string.
+*/
+itoa_cstring :: proc(a: ^Int, radix := i8(-1), allocator := context.allocator) -> (res: cstring, err: Error) {
+	assert_initialized(a);
+	/*
+		Radix defaults to 10.
+	*/
+	radix := radix if radix > 0 else 10;
+
+	s: string;
+	s, err = itoa_string(a, radix, true, allocator);
+	return cstring(raw_data(s)), err;
+}
+
+/*
+	A low-level `itoa` using a caller-provided buffer. `itoa_string` and `itoa_cstring` use this.
+	You can use also use it if you want to pre-allocate a buffer and optionally reuse it.
+
+	Use `radix_size` or `radix_size_estimate` to determine a buffer size big enough.
+
+	`written` includes the sign if negative, and the zero terminator if asked for.
+*/
+itoa_raw :: proc(a: ^Int, radix: i8, buffer: []u8, zero_terminate := false) -> (written: int, err: Error) {
+	assert_initialized(a);
+	/*
+		Radix defaults to 10.
+	*/
+	radix := radix if radix > 0 else 10;
+
+	/*
+		Early exit if we were given an empty buffer.
+	*/
+	available := len(buffer);
+	if available == 0 {
+		return 0, .Buffer_Overflow;
+	}
+	/*
+		Early exit if `Int` == 0 or the entire `Int` fits in a single radix digit.
+	*/
+	if is_zero(a) || (a.used == 1 && a.digit[0] < DIGIT(radix)) {
+		needed := 2 if is_neg(a) else 1;
+		needed += 1 if zero_terminate else 0;
+		if available < needed {
+			return 0, .Buffer_Overflow;
+		}
+
+		if is_neg(a) {
+			buffer[written] = '-';
+			written += 1;
+		}
+
+		buffer[written] = RADIX_TABLE[a.digit[0]];
+		written += 1;
+
+		if zero_terminate {
+			buffer[written] = 0;
+			written += 1;
+		}
+
+		return written, .OK;
+	}
+
+
+	/*
+		Fast path for radixes that are a power of two.
+	*/
+	if is_power_of_two(int(radix)) {
+
+
+
+		return len(buffer), .OK;
+	}
+
+	return -1, .Unimplemented;
+}
+
+itoa :: proc{itoa_string, itoa_raw};
+int_to_string  :: itoa;
+int_to_cstring :: itoa_cstring;
 
 /*
 	We size for `string`, not `cstring`.
 */
-radix_size :: proc(a: ^Int, radix: int) -> (size: int, err: Error) {
+radix_size :: proc(a: ^Int, radix: i8) -> (size: int, err: Error) {
 	t := a;
 
 	if radix < 2 || radix > 64 {
@@ -67,7 +183,7 @@ radix_size :: proc(a: ^Int, radix: int) -> (size: int, err: Error) {
  	t.sign = .Zero_or_Positive;
  	log: int;
 
- 	log, err = log_n(t, radix);
+ 	log, err = log_n(t, DIGIT(radix));
  	if err != .OK {
  		return log, err;
  	}
@@ -80,4 +196,19 @@ radix_size :: proc(a: ^Int, radix: int) -> (size: int, err: Error) {
  	} else {
  		return log + 1, .OK;
  	}
-}
+}
+
+/*
+	Characters used in radix conversions.
+*/
+RADIX_TABLE := "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+/";
+RADIX_TABLE_REVERSE := [80]u8{
+   0x3e, 0xff, 0xff, 0xff, 0x3f, 0x00, 0x01, 0x02, 0x03, 0x04, /* +,-./01234 */
+   0x05, 0x06, 0x07, 0x08, 0x09, 0xff, 0xff, 0xff, 0xff, 0xff, /* 56789:;<=> */
+   0xff, 0xff, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, /* ?@ABCDEFGH */
+   0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, /* IJKLMNOPQR */
+   0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0xff, 0xff, /* STUVWXYZ[\ */
+   0xff, 0xff, 0xff, 0xff, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, /* ]^_`abcdef */
+   0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, /* ghijklmnop */
+   0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, /* qrstuvwxyz */
+};