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263 lines
6.2 KiB
V
263 lines
6.2 KiB
V
// Copyright (c) 2019 Alexander Medvednikov. All rights reserved.
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// Use of this source code is governed by an MIT license
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// that can be found in the LICENSE file.
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// TODO: use optionals, or some way to return default with error.
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module strconv
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const(
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// int_size is the size in bits of an int or uint value.
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// int_size = 32 << (~u32(0) >> 63)
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// max_u64 = u64(u64(1 << 63) - 1)
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int_size = 32
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max_u64 = u64(C.UINT64_MAX) // use this until we add support
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)
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fn byte_to_lower(c byte) byte {
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return c | (`x` - `X`)
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}
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// parse_uint is like parse_int but for unsigned numbers.
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pub fn parse_uint(s string, _base int, _bit_size int) u64 {
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mut bit_size := _bit_size
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mut base := _base
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if s.len < 1 || !underscore_ok(s) {
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// return error('parse_uint: syntax error $s')
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return u64(0)
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}
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base0 := base == 0
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mut start_index := 0
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if 2 <= base && base <= 36 {
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// valid base; nothing to do
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} else if base == 0 {
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// Look for octal, hex prefix.
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base = 10
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if s[0] == `0` {
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if s.len >= 3 && byte_to_lower(s[1]) == `b` {
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base = 2
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start_index += 2
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}
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else if s.len >= 3 && byte_to_lower(s[1]) == `o` {
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base = 8
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start_index += 2
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}
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else if s.len >= 3 && byte_to_lower(s[1]) == `x` {
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base = 16
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start_index += 2
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}
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else {
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base = 8
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start_index++
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}
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}
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} else {
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// return error('parse_uint: base error $s - $base')
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return u64(0)
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}
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if bit_size == 0 {
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bit_size = int(int_size)
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} else if bit_size < 0 || bit_size > 64 {
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// return error('parse_uint: bitsize error $s - $bit_size')
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return u64(0)
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}
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// Cutoff is the smallest number such that cutoff*base > maxUint64.
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// Use compile-time constants for common cases.
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cutoff := u64(max_u64/u64(base)) + u64(1)
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max_val := if bit_size == 64 {
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max_u64
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} else {
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u64(u64(1)<<u64(bit_size))-u64(1)
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}
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mut underscores := false
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mut n := u64(0)
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for i in start_index..s.len {
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c := s[i]
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cl := byte_to_lower(c)
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mut d := byte(0)
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if c == `_` && base0 {
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// underscore_ok already called
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underscores = true
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continue
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}
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else if `0` <= c && c <= `9` { d = c - `0` }
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else if `a` <= cl && cl <= `z` { d = cl - `a` + 10 }
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else {
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// return error('parse_uint: syntax error $s')
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return u64(0)
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}
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if d >= byte(base) {
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// return error('parse_uint: syntax error $s')
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return u64(0)
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}
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if n >= cutoff {
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// n*base overflows
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// return error('parse_uint: range error $s')
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return max_val
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}
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n *= u64(base)
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n1 := n + u64(d)
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if n1 < n || n1 > max_val {
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// n+v overflows
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// return error('parse_uint: range error $s')
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return max_val
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}
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n = n1
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}
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if underscores && !underscore_ok(s) {
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// return error('parse_uint: syntax error $s')
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return u64(0)
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}
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return n
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}
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// parse_int interprets a string s in the given base (0, 2 to 36) and
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// bit size (0 to 64) and returns the corresponding value i.
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//
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// If the base argument is 0, the true base is implied by the string's
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// prefix: 2 for "0b", 8 for "0" or "0o", 16 for "0x", and 10 otherwise.
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// Also, for argument base 0 only, underscore characters are permitted
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// as defined by the Go syntax for integer literals.
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//
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// The bitSize argument specifies the integer type
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// that the result must fit into. Bit sizes 0, 8, 16, 32, and 64
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// correspond to int, int8, int16, int32, and int64.
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// If bitSize is below 0 or above 64, an error is returned.
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pub fn parse_int(_s string, base int, _bit_size int) i64 {
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mut s := _s
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mut bit_size := _bit_size
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if s.len < 1 {
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// return error('parse_int: syntax error $s')
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return i64(0)
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}
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// Pick off leading sign.
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mut neg := false
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if s[0] == `+` {
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s = s.right(1)
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} else if s[0] == `-` {
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neg = true
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s = s.right(1)
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}
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// Convert unsigned and check range.
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// un := parse_uint(s, base, bit_size) or {
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// return i64(0)
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// }
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un := parse_uint(s, base, bit_size)
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if un == 0 {
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return i64(0)
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}
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if bit_size == 0 {
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bit_size = int(int_size)
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}
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// TODO: check should u64(bit_size-1) be size of int (32)?
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cutoff := u64(u64(1) << u64(bit_size-1))
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if !neg && un >= cutoff {
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// return error('parse_int: range error $s0')
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return i64(cutoff - u64(1))
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}
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if neg && un > cutoff {
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// return error('parse_int: range error $s0')
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return -i64(cutoff)
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}
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return if neg { -i64(un) } else { i64(un) }
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}
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// atoi is equivalent to parse_int(s, 10, 0), converted to type int.
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pub fn atoi(s string) int {
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if (int_size == 32 && (0 < s.len && s.len < 10)) ||
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(int_size == 64 && (0 < s.len && s.len < 19)) {
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// Fast path for small integers that fit int type.
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mut start_idx := 0
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if s[0] == `-` || s[0] == `+` {
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start_idx++
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if s.len-start_idx < 1 {
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// return 0, &NumError{fnAtoi, s0, ErrSyntax}
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return 0
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}
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}
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mut n := 0
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for i in start_idx..s.len {
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ch := s[i] - `0`
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if ch > 9 {
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// return 0, &NumError{fnAtoi, s0, ErrSyntax}
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return 0
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}
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n = n*10 + int(ch)
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}
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return if s[0] == `-` { -n } else { n }
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}
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// Slow path for invalid, big, or underscored integers.
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int64 := parse_int(s, 10, 0)
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return int(int64)
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}
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// underscore_ok reports whether the underscores in s are allowed.
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// Checking them in this one function lets all the parsers skip over them simply.
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// Underscore must appear only between digits or between a base prefix and a digit.
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fn underscore_ok(s string) bool {
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// saw tracks the last character (class) we saw:
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// ^ for beginning of number,
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// 0 for a digit or base prefix,
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// _ for an underscore,
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// ! for none of the above.
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mut saw := `^`
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mut i := 0
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// Optional sign.
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if s.len >= 1 && (s[0] == `-` || s[0] == `+`) {
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i++
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}
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// Optional base prefix.
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mut hex := false
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if s.len-i >= 2 && s[i] == `0` &&
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(byte_to_lower(s[i+1]) == `b` || byte_to_lower(s[i+1]) == `o` || byte_to_lower(s[i+1]) == `x`) {
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saw = `0` // base prefix counts as a digit for "underscore as digit separator"
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hex = byte_to_lower(s[i+1]) == `x`
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i+=2
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}
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// Number proper.
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for ; i < s.len; i++ {
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// Digits are always okay.
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if (`0` <= s[i] && s[i] <= `9`) ||
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(hex && `a` <= byte_to_lower(s[i]) && byte_to_lower(s[i]) <= `f`) {
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saw = `0`
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continue
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}
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// Underscore must follow digit.
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if s[i] == `_` {
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if saw != `0` {
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return false
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}
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saw = `_`
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continue
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}
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// Underscore must also be followed by digit.
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if saw == `_` {
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return false
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}
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// Saw non-digit, non-underscore.
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saw = `!`
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}
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return saw != `_`
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}
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