path: root/pw_tokenizer/public/pw_tokenizer/tokenize.h

// Copyright 2020 The Pigweed Authors
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
#pragma once

#ifdef __cplusplus

#include <cstddef>
#include <cstdint>

#else

#include <assert.h>
#include <stddef.h>
#include <stdint.h>

#endif  // __cplusplus

#include "pw_preprocessor/arguments.h"
#include "pw_preprocessor/compiler.h"
#include "pw_preprocessor/concat.h"
#include "pw_preprocessor/util.h"
#include "pw_tokenizer/internal/argument_types.h"
#include "pw_tokenizer/internal/tokenize_string.h"

/// The type of the 32-bit token used in place of a string. Also available as
/// `pw::tokenizer::Token`.
typedef uint32_t pw_tokenizer_Token;

// Strings may optionally be tokenized to a domain. Strings in different
// domains can be processed separately by the token database tools. Each domain
// in use must have a corresponding section declared in the linker script. See
// `pw_tokenizer_linker_sections.ld` for more details.
//
// The default domain is an empty string.
#define PW_TOKENIZER_DEFAULT_DOMAIN ""

/// Converts a string literal to a `pw_tokenizer_Token` (`uint32_t`) token in a
/// standalone statement. C and C++ compatible. In C++, the string may be a
/// literal or a constexpr char array, including function variables like
/// `__func__`. In C, the argument must be a string literal. In either case, the
/// string must be null terminated, but may contain any characters (including
/// '\0').
///
/// @code
///
///   constexpr uint32_t token = PW_TOKENIZE_STRING("Any string literal!");
///
/// @endcode
#define PW_TOKENIZE_STRING(string_literal) \
  PW_TOKENIZE_STRING_DOMAIN(PW_TOKENIZER_DEFAULT_DOMAIN, string_literal)

/// Converts a string literal to a ``uint32_t`` token within an expression.
/// Requires C++.
///
/// @code
///
///   DoSomething(PW_TOKENIZE_STRING_EXPR("Succeed"));
///
/// @endcode
#define PW_TOKENIZE_STRING_EXPR(string_literal)                               \
  [&] {                                                                       \
    constexpr uint32_t lambda_ret_token = PW_TOKENIZE_STRING(string_literal); \
    return lambda_ret_token;                                                  \
  }()

/// Tokenizes a string literal in a standalone statement using the specified
/// @rstref{domain <module-pw_tokenizer-domains>}. C and C++ compatible.
#define PW_TOKENIZE_STRING_DOMAIN(domain, string_literal) \
  PW_TOKENIZE_STRING_MASK(domain, UINT32_MAX, string_literal)

/// Tokenizes a string literal using the specified @rstref{domain
/// <module-pw_tokenizer-domains>} within an expression. Requires C++.
#define PW_TOKENIZE_STRING_DOMAIN_EXPR(domain, string_literal) \
  [&] {                                                        \
    constexpr uint32_t lambda_ret_token =                      \
        PW_TOKENIZE_STRING_DOMAIN(domain, string_literal);     \
    return lambda_ret_token;                                   \
  }()

/// Tokenizes a string literal in a standalone statement using the specified
/// @rstref{domain <module-pw_tokenizer-domains>} and @rstref{bit mask
/// <module-pw_tokenizer-masks>}. C and C++ compatible.
#define PW_TOKENIZE_STRING_MASK(domain, mask, string_literal)                \
  /* assign to a variable */ _PW_TOKENIZER_MASK_TOKEN(mask, string_literal); \
                                                                             \
  static_assert(0 < (mask) && (mask) <= UINT32_MAX,                          \
                "Tokenizer masks must be non-zero uint32_t values.");        \
                                                                             \
  _PW_TOKENIZER_RECORD_ORIGINAL_STRING(                                      \
      _PW_TOKENIZER_MASK_TOKEN(mask, string_literal), domain, string_literal)

/// Tokenizes a string literal using the specified @rstref{domain
/// <module-pw_tokenizer-domains>} and @rstref{bit mask
/// <module-pw_tokenizer-masks>} within an expression. Requires C++.
#define PW_TOKENIZE_STRING_MASK_EXPR(domain, mask, string_literal) \
  [&] {                                                            \
    constexpr uint32_t lambda_ret_token =                          \
        PW_TOKENIZE_STRING_MASK(domain, mask, string_literal);     \
    return lambda_ret_token;                                       \
  }()

#define _PW_TOKENIZER_MASK_TOKEN(mask, string_literal) \
  ((pw_tokenizer_Token)(mask)&PW_TOKENIZER_STRING_TOKEN(string_literal))

/// Encodes a tokenized string and arguments to the provided buffer. The size of
/// the buffer is passed via a pointer to a `size_t`. After encoding is
/// complete, the `size_t` is set to the number of bytes written to the buffer.
///
/// The macro's arguments are equivalent to the following function signature:
///
/// @code
///
///   TokenizeToBuffer(void* buffer,
///                    size_t* buffer_size_pointer,
///                    const char* format,
///                    ...);  // printf-style arguments
/// @endcode
///
/// For example, the following encodes a tokenized string with a temperature to
/// a buffer. The buffer is passed to a function to send the message over a
/// UART.
///
/// @code
///
///   uint8_t buffer[32];
///   size_t size_bytes = sizeof(buffer);
///   PW_TOKENIZE_TO_BUFFER(
///       buffer, &size_bytes, "Temperature (C): %0.2f", temperature_c);
///   MyProject_EnqueueMessageForUart(buffer, size);
///
/// @endcode
///
/// While `PW_TOKENIZE_TO_BUFFER` is very flexible, it must be passed a buffer,
/// which increases its code size footprint at the call site.
#define PW_TOKENIZE_TO_BUFFER(buffer, buffer_size_pointer, format, ...) \
  PW_TOKENIZE_TO_BUFFER_DOMAIN(PW_TOKENIZER_DEFAULT_DOMAIN,             \
                               buffer,                                  \
                               buffer_size_pointer,                     \
                               format,                                  \
                               __VA_ARGS__)

/// Same as @c_macro{PW_TOKENIZE_TO_BUFFER}, but tokenizes to the specified
/// @rstref{domain <module-pw_tokenizer-domains>}.
#define PW_TOKENIZE_TO_BUFFER_DOMAIN(                 \
    domain, buffer, buffer_size_pointer, format, ...) \
  PW_TOKENIZE_TO_BUFFER_MASK(                         \
      domain, UINT32_MAX, buffer, buffer_size_pointer, format, __VA_ARGS__)

/// Same as @c_macro{PW_TOKENIZE_TO_BUFFER_DOMAIN}, but applies a
/// @rstref{bit mask <module-pw_tokenizer-masks>} to the token.
#define PW_TOKENIZE_TO_BUFFER_MASK(                               \
    domain, mask, buffer, buffer_size_pointer, format, ...)       \
  do {                                                            \
    PW_TOKENIZE_FORMAT_STRING(domain, mask, format, __VA_ARGS__); \
    _pw_tokenizer_ToBuffer(buffer,                                \
                           buffer_size_pointer,                   \
                           _pw_tokenizer_token,                   \
                           PW_TOKENIZER_ARG_TYPES(__VA_ARGS__)    \
                               PW_COMMA_ARGS(__VA_ARGS__));       \
  } while (0)

/// Converts a series of arguments to a compact format that replaces the format
/// string literal. Evaluates to a `pw_tokenizer_ArgTypes` value.
///
/// Depending on the size of `pw_tokenizer_ArgTypes`, the bottom 4 or 6 bits
/// store the number of arguments and the remaining bits store the types, two
/// bits per type. The arguments are not evaluated; only their types are used.
#define PW_TOKENIZER_ARG_TYPES(...) \
  PW_DELEGATE_BY_ARG_COUNT(_PW_TOKENIZER_TYPES_, __VA_ARGS__)

PW_EXTERN_C_START

// These functions encode the tokenized strings. These should not be called
// directly. Instead, use the corresponding PW_TOKENIZE_TO_* macros above.
void _pw_tokenizer_ToBuffer(void* buffer,
                            size_t* buffer_size_bytes,  // input and output arg
                            pw_tokenizer_Token token,
                            pw_tokenizer_ArgTypes types,
                            ...);

// This empty function allows the compiler to check the format string.
static inline void pw_tokenizer_CheckFormatString(const char* format, ...)
    PW_PRINTF_FORMAT(1, 2);

static inline void pw_tokenizer_CheckFormatString(const char* format, ...) {
  (void)format;
}

PW_EXTERN_C_END

/// Tokenizes a format string with optional arguments and sets the
/// `_pw_tokenizer_token` variable to the token. Must be used in its own scope,
/// since the same variable is used in every invocation.
///
/// The tokenized string uses the specified @rstref{tokenization domain
/// <module-pw_tokenizer-domains>}.  Use `PW_TOKENIZER_DEFAULT_DOMAIN` for the
/// default. The token also may be masked; use `UINT32_MAX` to keep all bits.
///
/// This macro checks that the printf-style format string matches the arguments,
/// stores the format string in a special section, and calculates the string's
/// token at compile time.
// clang-format off
#define PW_TOKENIZE_FORMAT_STRING(domain, mask, format, ...)                  \
  if (0) { /* Do not execute to prevent double evaluation of the arguments. */ \
    pw_tokenizer_CheckFormatString(format PW_COMMA_ARGS(__VA_ARGS__));         \
  }                                                                            \
                                                                               \
  /* Check that the macro is invoked with a supported number of arguments. */  \
  static_assert(                                                               \
      PW_FUNCTION_ARG_COUNT(__VA_ARGS__) <= PW_TOKENIZER_MAX_SUPPORTED_ARGS,   \
      "Tokenized strings cannot have more than "                               \
      PW_STRINGIFY(PW_TOKENIZER_MAX_SUPPORTED_ARGS) " arguments; "             \
      PW_STRINGIFY(PW_FUNCTION_ARG_COUNT(__VA_ARGS__))                         \
      " arguments were used for " #format " (" #__VA_ARGS__ ")");              \
                                                                               \
  /* Tokenize the string to a pw_tokenizer_Token at compile time. */           \
  static _PW_TOKENIZER_CONST pw_tokenizer_Token _pw_tokenizer_token =          \
      _PW_TOKENIZER_MASK_TOKEN(mask, format);                                  \
                                                                               \
  _PW_TOKENIZER_RECORD_ORIGINAL_STRING(_pw_tokenizer_token, domain, format)

// clang-format on

// Creates unique names to use for tokenized string entries and linker sections.
#define _PW_TOKENIZER_UNIQUE(prefix) PW_CONCAT(prefix, __LINE__, _, __COUNTER__)

#ifdef __cplusplus

#define _PW_TOKENIZER_CONST constexpr

#define _PW_TOKENIZER_RECORD_ORIGINAL_STRING(token, domain, string)            \
  alignas(1) static constexpr auto _PW_TOKENIZER_SECTION _PW_TOKENIZER_UNIQUE( \
      _pw_tokenizer_string_entry_) =                                           \
      ::pw::tokenizer::internal::MakeEntry(token, domain, string)

namespace pw {
namespace tokenizer {

using Token = ::pw_tokenizer_Token;

}  // namespace tokenizer
}  // namespace pw

#else

#define _PW_TOKENIZER_CONST const

#define _PW_TOKENIZER_RECORD_ORIGINAL_STRING(token, domain, string) \
  _Alignas(1) static const _PW_TOKENIZER_STRING_ENTRY(token, domain, string)

#endif  // __cplusplus

// _PW_TOKENIZER_SECTION places the tokenized strings in a special .pw_tokenizer
// linker section. Host-side decoding tools read the strings and tokens from
// this section to build a database of tokenized strings.
//
// This section should be declared as type INFO so that it is excluded from the
// final binary. To declare the section, as well as the .pw_tokenizer.info
// metadata section, add the following to the linker script's SECTIONS command:
//
//   .pw_tokenizer.info 0x0 (INFO) :
//   {
//     KEEP(*(.pw_tokenizer.info))
//   }
//
//   .pw_tokenizer.entries 0x0 (INFO) :
//   {
//     KEEP(*(.pw_tokenizer.entries.*))
//   }
//
// A linker script snippet that provides these sections is provided in the file
// pw_tokenizer_linker_sections.ld. This file may be directly included into
// existing linker scripts.
//
// The tokenized string sections can also be managed without linker script
// modifications, though this is not recommended. The section can be extracted
// and removed from the ELF with objcopy:
//
//   objcopy --only-section .pw_tokenizer.* <ORIGINAL_ELF> <OUTPUT_ELF>
//   objcopy --remove-section .pw_tokenizer.* <ORIGINAL_ELF>
//
// OUTPUT_ELF will be an ELF with only the tokenized strings, and the original
// ELF file will have the sections removed.
//
// Without the above linker script modifications, the section garbage collection
// option (--gc-sections) removes the tokenized string sections. To avoid
// editing the target linker script, a separate metadata ELF can be linked
// without --gc-sections to preserve the tokenized data.
//
// pw_tokenizer is intended for use with ELF files only. Mach-O files (macOS
// executables) do not support section names longer than 16 characters, so a
// short, unused section name is used on macOS.
#ifdef __APPLE__
#define _PW_TOKENIZER_SECTION \
  PW_KEEP_IN_SECTION(PW_STRINGIFY(_PW_TOKENIZER_UNIQUE(.pw.)))
#else
#define _PW_TOKENIZER_SECTION \
  PW_KEEP_IN_SECTION(PW_STRINGIFY(_PW_TOKENIZER_UNIQUE(.pw_tokenizer.entries.)))
#endif  // __APPLE__