//===-- 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/stdint_proxy.h" #include "hdr/types/size_t.h" #include "src/__support/common.h" #include "src/__support/ctype_utils.h" #include "src/__support/macros/config.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(result); } } // namespace LIBC_NAMESPACE_DECL