big: Add ASCII file import/export.

3 files changed, 84 insertions, 13 deletions

diff --git a/core/math/big/common.odin b/core/math/big/common.odin
index fb215cd69..11810d144 100644
--- a/core/math/big/common.odin
+++ b/core/math/big/common.odin
@@ -166,6 +166,10 @@ Error :: enum int {
 	Division_by_Zero        = 8,
 	Math_Domain_Error       = 9,
 
+	Cannot_Open_File        = 50,
+	Cannot_Read_File        = 51,
+	Cannot_Write_File       = 52,
+
 	Unimplemented           = 127,
 };
 
diff --git a/core/math/big/example.odin b/core/math/big/example.odin
index 6b697d472..dfc49bc15 100644
--- a/core/math/big/example.odin
+++ b/core/math/big/example.odin
@@ -86,7 +86,7 @@ print :: proc(name: string, a: ^Int, base := i8(10), print_name := true, newline
 	}
 }
 
-// printf :: fmt.printf;
+printf :: fmt.printf;
 
 demo :: proc() {
 	a, b, c, d, e, f, res := &Int{}, &Int{}, &Int{}, &Int{}, &Int{}, &Int{}, &Int{};
@@ -107,6 +107,18 @@ demo :: proc() {
 	print("a(10): ", a, 10, true, true, true);
 	fmt.printf("err: %v\n", err);
 	fmt.printf("RANDOM_PRIME_ITERATIONS_USED: %v\n", RANDOM_PRIME_ITERATIONS_USED);
+
+	// err = internal_int_write_to_ascii_file(a, "a.txt");
+	// if err != nil {
+	// 	fmt.printf("internal_int_write_to_ascii_file returned %v\n", err);
+	// }
+
+	// err = internal_int_read_from_ascii_file(b, "a.txt");
+	// if err != nil {
+	// 	fmt.printf("internal_int_read_from_ascii_file returned %v\n", err);
+	// }
+
+	// print("b: ", b);
 }
 
 main :: proc() {
diff --git a/core/math/big/radix.odin b/core/math/big/radix.odin
index 76854e244..fb1af250b 100644
--- a/core/math/big/radix.odin
+++ b/core/math/big/radix.odin
@@ -16,20 +16,18 @@ package math_big
 
 import "core:intrinsics"
 import "core:mem"
+import "core:os"
 
 /*
-	This version of `itoa` allocates one behalf of the caller. The caller must free the string.
+	This version of `itoa` allocates on behalf of the caller. The caller must free the string.
+	The radix defaults to 10.
 */
-int_itoa_string :: proc(a: ^Int, radix := i8(-1), zero_terminate := false, allocator := context.allocator) -> (res: string, err: Error) {
+int_itoa_string :: proc(a: ^Int, radix := i8(10), zero_terminate := false, allocator := context.allocator) -> (res: string, err: Error) {
 	assert_if_nil(a);
 	context.allocator = allocator;
 
 	a := a; radix := radix;
 	clear_if_uninitialized(a) or_return;
-	/*
-		Radix defaults to 10.
-	*/
-	radix = radix if radix > 0 else 10;
 
 	/*
 		TODO: If we want to write a prefix for some of the radixes, we can oversize the buffer.
@@ -57,18 +55,15 @@ int_itoa_string :: proc(a: ^Int, radix := i8(-1), zero_terminate := false, alloc
 }
 
 /*
-	This version of `itoa` allocates one behalf of the caller. The caller must free the string.
+	This version of `itoa` allocates on behalf of the caller. The caller must free the string.
+	The radix defaults to 10.
 */
-int_itoa_cstring :: proc(a: ^Int, radix := i8(-1), allocator := context.allocator) -> (res: cstring, err: Error) {
+int_itoa_cstring :: proc(a: ^Int, radix := i8(10), allocator := context.allocator) -> (res: cstring, err: Error) {
 	assert_if_nil(a);
 	context.allocator = allocator;
 
 	a := a; radix := radix;
 	clear_if_uninitialized(a) or_return;
-	/*
-		Radix defaults to 10.
-	*/
-	radix = radix if radix > 0 else 10;
 
 	s: string;
 	s, err = int_itoa_string(a, radix, true);
@@ -378,6 +373,66 @@ radix_size :: proc(a: ^Int, radix: i8, zero_terminate := false, allocator := con
 }
 
 /*
+	We might add functions to read and write byte-encoded Ints from/to files, using `int_to_bytes_*` functions.
+
+	LibTomMath allows exporting/importing to/from a file in ASCII, but it doesn't support a much more compact representation in binary, even though it has several pack functions int_to_bytes_* (which I expanded upon and wrote Python interoperable versions of as well), and (un)pack, which is GMP compatible.
+	Someone could implement their own read/write binary int procedures, of course.
+
+	Could be worthwhile to add a canonical binary file representation with an optional small header that says it's an Odin big.Int, big.Rat or Big.Float, byte count for each component that follows, flag for big/little endian and a flag that says a checksum exists at the end of the file.
+	For big.Rat and big.Float the header couldn't be optional, because we'd have no way to distinguish where the components end.
+*/
+
+/*
+	Read an Int from an ASCII file.
+*/
+internal_int_read_from_ascii_file :: proc(a: ^Int, filename: string, radix := i8(10), allocator := context.allocator) -> (err: Error) {
+	context.allocator = allocator;
+
+	/*
+		We can either read the entire file at once, or read a bunch at a time and keep multiplying by the radix.
+		For now, we'll read the entire file. Eventually we'll replace this with a copy that duplicates the logic
+		of `atoi` so we don't need to read the entire file.
+	*/
+
+	res, ok := os.read_entire_file(filename, allocator);
+	defer delete(res, allocator);
+
+	if !ok {
+		return .Cannot_Read_File;
+	}
+
+	as := string(res);
+	return atoi(a, as, radix);
+}
+
+/*
+	Write an Int to an ASCII file.
+*/
+internal_int_write_to_ascii_file :: proc(a: ^Int, filename: string, radix := i8(10), allocator := context.allocator) -> (err: Error) {
+	context.allocator = allocator;
+
+	/*
+		For now we'll convert the Int using itoa and writing the result in one go.
+		If we want to preserve memory we could duplicate the itoa logic and write backwards.
+	*/
+
+	as := itoa(a, radix) or_return;
+	defer delete(as);
+
+	l := len(as);
+	assert(l > 0);
+
+	data := transmute([]u8)mem.Raw_Slice{
+		data = raw_data(as),
+		len  = l,
+	};
+
+	ok := os.write_entire_file(name=filename, data=data, truncate=true);
+	return nil if ok else .Cannot_Write_File;
+}
+
+
+/*
 	Overestimate the size needed for the bigint to string conversion by a very small amount.
 	The error is about 10^-8; it will overestimate the result by at most 11 elements for
 	a number of the size 2^(2^31)-1 which is currently the largest possible in this library.