120689e466
Functions like isalpha / tolower can operate on chars internally. This allows us to get rid of unnecessary casts and open a way to creating wchar_t overloads with the same names (e.g. for isalpha), that would simplify templated code for conversion functions (see 315dfe5865962d8a3d60e21d1fffce5214fe54ef). Add the int->char converstion to public entrypoints implementation instead. We also need to introduce bounds check on the input argument values - these functions' behavior is unspecified if the argument is neither EOF nor fits in "unsigned char" range, but the tests we've had verified that they always return false for small negative values. To preserve this behavior, cover it explicitly.
62 lines
2.4 KiB
C++
62 lines
2.4 KiB
C++
//===-- Implementation of l64a --------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "src/stdlib/l64a.h"
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#include "hdr/stdint_proxy.h"
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#include "hdr/types/size_t.h"
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#include "src/__support/common.h"
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#include "src/__support/ctype_utils.h"
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#include "src/__support/libc_assert.h"
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#include "src/__support/macros/config.h"
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namespace LIBC_NAMESPACE_DECL {
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// the standard says to only use up to 6 characters. Null terminator is
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// unnecessary, but we'll add it for ease-of-use. Also going from 48 -> 56 bits
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// probably won't matter since it's likely 32-bit aligned anyways.
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constexpr size_t MAX_BASE64_LENGTH = 6;
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LIBC_THREAD_LOCAL char BASE64_BUFFER[MAX_BASE64_LENGTH + 1];
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constexpr static char b64_int_to_char(uint32_t num) {
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// from the standard: "The characters used to represent digits are '.' (dot)
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// for 0, '/' for 1, '0' through '9' for [2,11], 'A' through 'Z' for [12,37],
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// and 'a' through 'z' for [38,63]."
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LIBC_ASSERT(num < 64);
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if (num == 0)
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return '.';
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if (num == 1)
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return '/';
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if (num < 38)
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return internal::toupper(internal::int_to_b36_char(num - 2));
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// this tolower is technically unnecessary, but it provides safety if we
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// change the default behavior of int_to_b36_char. Also the compiler
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// completely elides it so there's no performance penalty, see:
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// https://godbolt.org/z/o5ennv7fc
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return internal::tolower(internal::int_to_b36_char(num - 2 - 26));
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}
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// This function takes a long and converts the low 32 bits of it into at most 6
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// characters. It's returned as a pointer to a static buffer.
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LLVM_LIBC_FUNCTION(char *, l64a, (long value)) {
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// static cast to uint32_t to get just the low 32 bits in a consistent way.
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// The standard says negative values are undefined, so I'm just defining them
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// to be treated as unsigned.
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uint32_t cur_value = static_cast<uint32_t>(value);
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for (size_t i = 0; i < MAX_BASE64_LENGTH; ++i) {
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uint32_t cur_char = cur_value % 64;
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BASE64_BUFFER[i] = b64_int_to_char(cur_char);
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cur_value /= 64;
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}
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BASE64_BUFFER[MAX_BASE64_LENGTH] = '\0'; // force null termination.
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return BASE64_BUFFER;
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}
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} // namespace LIBC_NAMESPACE_DECL
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