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big: Add int_from_bytes_*.

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This commit is contained in:
Jeroen van Rijn
2021-08-11 20:59:54 +02:00
parent ee24f2dd37
commit eb22a49b02
2 changed files with 182 additions and 10 deletions
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core/math/big/helpers.odin
+138 -3
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@@ -12,6 +12,8 @@ package math_big
import "core:intrinsics"
import rnd "core:math/rand"
// import "core:fmt"
/*
TODO: Int.flags and Constants like ONE, NAN, etc, are not yet properly handled everywhere.
*/
@@ -608,16 +610,17 @@ int_from_bytes_big :: proc(a: ^Int, buf: []u8, signed := false, allocator := con
if l == 0 { return .Invalid_Argument; }
sign: Sign;
size_in_bits := l * 8;
size_in_bits := l * 8;
if signed {
/*
First byte denotes the sign.
*/
size_in_bits -= 8;
}
size_in_digits := size_in_bits / _DIGIT_BITS;
size_in_digits := (size_in_bits + _DIGIT_BITS - 1) / _DIGIT_BITS;
size_in_digits += 0 if size_in_bits % 8 == 0 else 1;
if err = internal_grow(a, size_in_digits); err != nil { return err; }
if err = internal_zero(a, false, allocator); err != nil { return err; }
if err = internal_grow(a, size_in_digits, false, allocator); err != nil { return err; }
if signed {
sign = .Zero_or_Positive if buf[0] == 0 else .Negative;
@@ -629,9 +632,141 @@ int_from_bytes_big :: proc(a: ^Int, buf: []u8, signed := false, allocator := con
a.digit[0] |= DIGIT(v);
}
a.sign = sign;
a.used = size_in_digits;
return internal_clamp(a);
}
/*
Read `Int` from a Big Endian Python binary representation.
Sign is detected from the first byte if `signed` is true.
*/
int_from_bytes_big_python :: proc(a: ^Int, buf: []u8, signed := false, allocator := context.allocator) -> (err: Error) {
assert_if_nil(a);
buf := buf;
l := len(buf);
if l == 0 { return .Invalid_Argument; }
sign: Sign;
size_in_bits := l * 8;
if signed {
/*
First byte denotes the sign.
*/
size_in_bits -= 8;
}
size_in_digits := (size_in_bits + _DIGIT_BITS - 1) / _DIGIT_BITS;
size_in_digits += 0 if size_in_bits % 8 == 0 else 1;
if err = internal_zero(a, false, allocator); err != nil { return err; }
if err = internal_grow(a, size_in_digits, false, allocator); err != nil { return err; }
if signed {
sign = .Zero_or_Positive if buf[0] == 0 else .Negative;
buf = buf[1:];
}
for v in buf {
if err = internal_shl(a, a, 8); err != nil { return err; }
if signed && sign == .Negative {
a.digit[0] |= DIGIT(255 - v);
} else {
a.digit[0] |= DIGIT(v);
}
}
a.sign = sign;
a.used = size_in_digits;
if err = internal_clamp(a); err != nil { return err; }
if signed && sign == .Negative {
return internal_sub(a, a, 1);
}
return nil;
}
/*
Read `Int` from a Little Endian binary representation.
Sign is detected from the last byte if `signed` is true.
*/
int_from_bytes_little :: proc(a: ^Int, buf: []u8, signed := false, allocator := context.allocator) -> (err: Error) {
assert_if_nil(a);
buf := buf;
l := len(buf);
if l == 0 { return .Invalid_Argument; }
sign: Sign;
size_in_bits := l * 8;
if signed {
/*
First byte denotes the sign.
*/
size_in_bits -= 8;
}
size_in_digits := (size_in_bits + _DIGIT_BITS - 1) / _DIGIT_BITS;
size_in_digits += 0 if size_in_bits % 8 == 0 else 1;
if err = internal_zero(a, false, allocator); err != nil { return err; }
if err = internal_grow(a, size_in_digits, false, allocator); err != nil { return err; }
if signed {
sign = .Zero_or_Positive if buf[l-1] == 0 else .Negative;
buf = buf[:l-1];
l -= 1;
}
for _, i in buf {
if err = internal_shl(a, a, 8); err != nil { return err; }
a.digit[0] |= DIGIT(buf[l-i-1]);
}
a.sign = sign;
a.used = size_in_digits;
return internal_clamp(a);
}
/*
Read `Int` from a Little Endian Python binary representation.
Sign is detected from the first byte if `signed` is true.
*/
int_from_bytes_little_python :: proc(a: ^Int, buf: []u8, signed := false, allocator := context.allocator) -> (err: Error) {
assert_if_nil(a);
buf := buf;
l := len(buf);
if l == 0 { return .Invalid_Argument; }
sign: Sign;
size_in_bits := l * 8;
if signed {
/*
First byte denotes the sign.
*/
size_in_bits -= 8;
}
size_in_digits := (size_in_bits + _DIGIT_BITS - 1) / _DIGIT_BITS;
size_in_digits += 0 if size_in_bits % 8 == 0 else 1;
if err = internal_zero(a, false, allocator); err != nil { return err; }
if err = internal_grow(a, size_in_digits, false, allocator); err != nil { return err; }
if signed {
sign = .Zero_or_Positive if buf[l-1] == 0 else .Negative;
buf = buf[:l-1];
l -= 1;
}
for _, i in buf {
if err = internal_shl(a, a, 8); err != nil { return err; }
if signed && sign == .Negative {
a.digit[0] |= DIGIT(255 - buf[l-i-1]);
} else {
a.digit[0] |= DIGIT(buf[l-i-1]);
}
}
a.sign = sign;
a.used = size_in_digits;
if err = internal_clamp(a); err != nil { return err; }
if signed && sign == .Negative {
return internal_sub(a, a, 1);
}
return nil;
}
/*
Initialize constants.
*/