libc/src/stdio/printf_core/writer.h

   1 //===-- Writer definition for printf ----------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_LIBC_SRC_STDIO_PRINTF_CORE_WRITER_H
  10 #define LLVM_LIBC_SRC_STDIO_PRINTF_CORE_WRITER_H
  11
  12 #include "src/__support/CPP/string_view.h"
  13 #include <stddef.h>
  14
  15 namespace __llvm_libc {
  16 namespace printf_core {
  17
  18 using WriteStrFunc = int (*)(void *, cpp::string_view);
  19 using WriteCharsFunc = int (*)(void *, char, size_t);
  20 using WriteCharFunc = int (*)(void *, char);
  21
  22 class Writer final {
  23   // output is a pointer to the string or file that the writer is meant to write
  24   // to.
  25   void *output;
  26
  27   // raw_write is a function that, when called on output with a char* and
  28   // length, will copy the number of bytes equal to the length from the char*
  29   // onto the end of output. It should return a positive number or zero on
  30   // success, or a negative number on failure.
  31   WriteStrFunc str_write;
  32   WriteCharsFunc chars_write;
  33   WriteCharFunc char_write;
  34
  35   int chars_written = 0;
  36
  37 public:
  38   Writer(void *init_output, WriteStrFunc init_str_write,
  39          WriteCharsFunc init_chars_write, WriteCharFunc init_char_write)
  40       : output(init_output), str_write(init_str_write),
  41         chars_write(init_chars_write), char_write(init_char_write) {}
  42
  43   // write will copy new_string into output using str_write. It increments
  44   // chars_written by the length of new_string. It returns the result of
  45   // str_write.
  46   int write(cpp::string_view new_string);
  47
  48   // this version of write will copy length copies of new_char into output using
  49   // chars_write. This is primarily used for padding.  It returns the result of
  50   // chars_write.
  51   int write(char new_char, size_t len);
  52
  53   // this version of write will copy just new_char into output. This is often
  54   // used for negative signs. It returns the result of chars_write.
  55   int write(char new_char);
  56
  57   int get_chars_written() { return chars_written; }
  58 };
  59
  60 } // namespace printf_core
  61 } // namespace __llvm_libc
  62
  63 #endif // LLVM_LIBC_SRC_STDIO_PRINTF_CORE_WRITER_H