66 lines
2.3 KiB
C++
66 lines
2.3 KiB
C++
//===-- Implementation of a64l --------------------------------------------===//
|
|
//
|
|
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
|
|
// See https://llvm.org/LICENSE.txt for license information.
|
|
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "src/stdlib/a64l.h"
|
|
#include "hdr/types/size_t.h"
|
|
#include "src/__support/common.h"
|
|
#include "src/__support/ctype_utils.h"
|
|
#include "src/__support/macros/config.h"
|
|
|
|
#include <stdint.h>
|
|
|
|
namespace LIBC_NAMESPACE_DECL {
|
|
|
|
// I'm not sure this should go in ctype_utils since the specific ordering of
|
|
// base64 is so very implementation specific, and also this set is unusual.
|
|
// Returns -1 on any char without a specified value.
|
|
constexpr static int32_t b64_char_to_int(char ch) {
|
|
// from the standard: "The characters used to represent digits are '.' (dot)
|
|
// for 0, '/' for 1, '0' through '9' for [2,11], 'A' through 'Z' for [12,37],
|
|
// and 'a' through 'z' for [38,63]."
|
|
if (ch == '.')
|
|
return 0;
|
|
if (ch == '/')
|
|
return 1;
|
|
|
|
// handle the case of an unspecified char.
|
|
if (!internal::isalnum(ch))
|
|
return -1;
|
|
|
|
bool is_lower = internal::islower(ch);
|
|
// add 2 to account for '.' and '/', then b36_char_to_int is case insensitive
|
|
// so add case sensitivity back.
|
|
return internal::b36_char_to_int(ch) + 2 + (is_lower ? 26 : 0);
|
|
}
|
|
|
|
// This function takes a base 64 string and writes it to the low 32 bits of a
|
|
// long.
|
|
// TODO: use LIBC_ADD_NULL_CHECKS for checking if the input is a null pointer.
|
|
LLVM_LIBC_FUNCTION(long, a64l, (const char *s)) {
|
|
// the standard says to only use up to 6 characters.
|
|
constexpr size_t MAX_LENGTH = 6;
|
|
int32_t result = 0;
|
|
|
|
for (size_t i = 0; i < MAX_LENGTH && s[i] != '\0'; ++i) {
|
|
int32_t cur_val = b64_char_to_int(s[i]);
|
|
// The standard says what happens on an unspecified character is undefined,
|
|
// here we treat it as the end of the string.
|
|
if (cur_val == -1)
|
|
break;
|
|
|
|
// the first digit is the least significant, so for each subsequent digit we
|
|
// shift it more. 6 bits since 2^6 = 64
|
|
result += (cur_val << (6 * i));
|
|
}
|
|
|
|
// standard says to sign extend from 32 bits.
|
|
return static_cast<long>(result);
|
|
}
|
|
|
|
} // namespace LIBC_NAMESPACE_DECL
|