//===-- Implementation of l64a --------------------------------------------===// // // 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/l64a.h" #include "hdr/types/size_t.h" #include "src/__support/common.h" #include "src/__support/ctype_utils.h" #include "src/__support/libc_assert.h" #include "src/__support/macros/config.h" #include namespace LIBC_NAMESPACE_DECL { // the standard says to only use up to 6 characters. Null terminator is // unnecessary, but we'll add it for ease-of-use. Also going from 48 -> 56 bits // probably won't matter since it's likely 32-bit aligned anyways. constexpr size_t MAX_BASE64_LENGTH = 6; LIBC_THREAD_LOCAL char BASE64_BUFFER[MAX_BASE64_LENGTH + 1]; constexpr static char b64_int_to_char(uint32_t num) { // 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]." LIBC_ASSERT(num < 64); if (num == 0) return '.'; if (num == 1) return '/'; if (num < 38) return static_cast( internal::toupper(internal::int_to_b36_char(num - 2))); // this tolower is technically unnecessary, but it provides safety if we // change the default behavior of int_to_b36_char. Also the compiler // completely elides it so there's no performance penalty, see: // https://godbolt.org/z/o5ennv7fc return static_cast( internal::tolower(internal::int_to_b36_char(num - 2 - 26))); } // This function takes a long and converts the low 32 bits of it into at most 6 // characters. It's returned as a pointer to a static buffer. LLVM_LIBC_FUNCTION(char *, l64a, (long value)) { // static cast to uint32_t to get just the low 32 bits in a consistent way. // The standard says negative values are undefined, so I'm just defining them // to be treated as unsigned. uint32_t cur_value = static_cast(value); for (size_t i = 0; i < MAX_BASE64_LENGTH; ++i) { uint32_t cur_char = cur_value % 64; BASE64_BUFFER[i] = b64_int_to_char(cur_char); cur_value /= 64; } BASE64_BUFFER[MAX_BASE64_LENGTH] = '\0'; // force null termination. return BASE64_BUFFER; } } // namespace LIBC_NAMESPACE_DECL