[libc] add fprintf and file_writer

[michaelrj]

Summary

This patch adds the file_writer header, which just provides a wrapper
for File->write, as well as fprintf to use it. There are no unit tests
for file_writer since it's too simple to need them, but fprintf does
have a simple test of writing to a file.

[sivachandra]

libc/src/stdio/printf_core/file_writer.h

24

Is it OK to ignore the return value? For example, if file were read only, then write would fail. Shouldn't that be reflected in the fprintf return value?

[michaelrj]

add handling for FILE errors

libc/src/stdio/printf_core/file_writer.h

24

I've added a check of the file's ferror status in fprintf and a section of the test to check that it works.

[sivachandra]

libc/test/src/stdio/fprintf_test.cpp

30

Put this is a common constexpr char[].

33

Same here.

45

Instead of 37, use sizeof(...).

[michaelrj]

move to constexpr variables for test strings

libc/config/linux/x86_64/entrypoints.txt

list(APPEND TARGET_LIBC_ENTRYPOINTS
     libc.src.stdio.fread
     libc.src.stdio.fread_unlocked
     libc.src.stdio.fseek
     libc.src.stdio.funlockfile
     libc.src.stdio.fwrite
     libc.src.stdio.fwrite_unlocked
     libc.src.stdio.sprintf
     libc.src.stdio.snprintf
+    libc.src.stdio.fprintf
     libc.src.stdio.stderr
     libc.src.stdio.stdout
 
     # signal.h entrypoints
     # TODO: Enable signal.h entrypoints after fixing signal.h
     # libc.src.signal.raise
     # libc.src.signal.sigaction
     # libc.src.signal.sigdelset

libc/src/stdio/CMakeLists.txt

SRCS
     snprintf.cpp
   HDRS
     snprintf.h
   DEPENDS
     libc.src.stdio.printf_core.printf_main
     libc.src.stdio.printf_core.string_writer
     libc.src.stdio.printf_core.writer
 )
+
+add_entrypoint_object(
+  fprintf
+  SRCS
+    fprintf.cpp
+  HDRS
+    fprintf.h
+  DEPENDS
+    libc.include.stdio
+    libc.src.stdio.printf_core.printf_main
+    libc.src.stdio.printf_core.file_writer
+    libc.src.stdio.printf_core.writer
+)

libc/src/stdio/fprintf.h

+//===-- Implementation header of fprintf ------------------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_STDIO_FPRINTF_H
+#define LLVM_LIBC_SRC_STDIO_FPRINTF_H
+
+#include <stdio.h>
+
+namespace __llvm_libc {
+
+int fprintf(::FILE *__restrict stream, const char *__restrict format, ...);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_STDIO_FPRINTF_H

libc/src/stdio/fprintf.cpp

+//===-- Implementation of fprintf -------------------------------*- C++ -*-===//
+//
+// 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/stdio/fprintf.h"
+
+#include "src/__support/arg_list.h"
+#include "src/stdio/ferror.h"
+#include "src/stdio/printf_core/file_writer.h"
+#include "src/stdio/printf_core/printf_main.h"
+#include "src/stdio/printf_core/writer.h"
+
+#include <stdarg.h>
+#include <stdio.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, fprintf,
+                   (::FILE *__restrict stream, const char *__restrict format,
+                    ...)) {
+  va_list vlist;
+  va_start(vlist, format);
+  internal::ArgList args(vlist); // This holder class allows for easier copying
+                                 // and pointer semantics, as well as handling
+                                 // destruction automatically.
+  va_end(vlist);
+  printf_core::Writer writer(reinterpret_cast<void *>(stream),
+                             printf_core::write_to_file);
+
+  int ret_val = printf_core::printf_main(&writer, format, args);
+  if (__llvm_libc::ferror(stream))
+    return -1;
+  return ret_val;
+}
+
+} // namespace __llvm_libc

libc/src/stdio/printf_core/CMakeLists.txt

 add_header_library(
   string_writer
   HDRS
     string_writer.h
   DEPENDS
     libc.src.string.memory_utils.memcpy_implementation
 )
 
+add_header_library(
+  file_writer
+  HDRS
+    file_writer.h
+  DEPENDS
+    libc.src.__support.File.file
+)
+
 add_object_library(
   writer
   SRCS
     writer.cpp
   HDRS
     writer.h
   DEPENDS
     libc.src.string.memory_utils.memset_implementation

libc/src/stdio/printf_core/file_writer.h

+//===-- FILE Writer class for printf ----------------------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_STDIO_PRINTF_CORE_FILE_WRITER_H
+#define LLVM_LIBC_SRC_STDIO_PRINTF_CORE_FILE_WRITER_H
+
+#include "src/__support/File/file.h"
+#include <stddef.h>
+
+namespace __llvm_libc {
+namespace printf_core {
+
+// write_to_file treats raw_pointer as a File and calls its write
+// function.
+void write_to_file(void *raw_pointer, const char *__restrict to_write,
+                   size_t len) {
+  __llvm_libc::File *file = reinterpret_cast<__llvm_libc::File *>(raw_pointer);
+  file->write(to_write, len);
+}
+
+} // namespace printf_core
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_STDIO_PRINTF_CORE_FILE_WRITER_H

libc/test/src/stdio/CMakeLists.txt

add_libc_unittest(
   SUITE
     libc_stdio_unittests
   SRCS
     snprintf_test.cpp
   DEPENDS
     libc.src.stdio.snprintf
 )
 
+add_libc_unittest(
+  fprintf_test
+  SUITE
+    libc_stdio_unittests
+  SRCS
+    fprintf_test.cpp
+  DEPENDS
+    libc.src.stdio.fprintf
+    libc.src.stdio.fclose
+    libc.src.stdio.ferror
+    libc.src.stdio.fopen
+    libc.src.stdio.fread
+)
+
 add_subdirectory(printf_core)
 
 add_subdirectory(testdata)

libc/test/src/stdio/fprintf_test.cpp

+//===-- Unittests for fprintf ---------------------------------------------===//
+//
+// 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/stdio/fclose.h"
+#include "src/stdio/ferror.h"
+#include "src/stdio/fopen.h"
+#include "src/stdio/fread.h"
+
+#include "src/stdio/fprintf.h"
+
+#include "utils/UnitTest/Test.h"
+
+#include <errno.h>
+#include <stdio.h>
+
+TEST(LlvmLibcFPrintfTest, WriteToFile) {
+  constexpr char FILENAME[] = "testdata/fprintf_output.test";
+  ::FILE *file = __llvm_libc::fopen(FILENAME, "w");
+  ASSERT_FALSE(file == nullptr);
+
+  int written;
+
+  constexpr char simple[] = "A simple string with no conversions.\n";
+  written = __llvm_libc::fprintf(file, simple);
+  EXPECT_EQ(written, 37);
+
+  constexpr char numbers[] = "1234567890\n";
+  written = __llvm_libc::fprintf(file, "%s", numbers);
+  EXPECT_EQ(written, 11);
+
+  constexpr char format_more[] = "%s and more\n";
+  constexpr char short_numbers[] = "1234";
+  written = __llvm_libc::fprintf(file, format_more, short_numbers);
+  EXPECT_EQ(written, 14);
+
+  ASSERT_EQ(0, __llvm_libc::fclose(file));
+
+  file = __llvm_libc::fopen(FILENAME, "r");
+  ASSERT_FALSE(file == nullptr);
+
+  char data[50];
+  ASSERT_EQ(__llvm_libc::fread(data, 1, sizeof(simple) - 1, file),
+            sizeof(simple) - 1);
+  data[sizeof(simple) - 1] = '\0';
+  ASSERT_STREQ(data, simple);
+  ASSERT_EQ(__llvm_libc::fread(data, 1, sizeof(numbers) - 1, file),
+            sizeof(numbers) - 1);
+  data[sizeof(numbers) - 1] = '\0';
+  ASSERT_STREQ(data, numbers);
+  ASSERT_EQ(__llvm_libc::fread(
+                data, 1, sizeof(format_more) + sizeof(short_numbers) - 4, file),
+            sizeof(format_more) + sizeof(short_numbers) - 4);
+  data[sizeof(format_more) + sizeof(short_numbers) - 4] = '\0';
+  ASSERT_STREQ(data, "1234 and more\n");
+
+  ASSERT_EQ(__llvm_libc::ferror(file), 0);
+
+  written =
+      __llvm_libc::fprintf(file, "Writing to a read only file should fail.");
+  EXPECT_EQ(written, -1);
+
+  ASSERT_EQ(__llvm_libc::fclose(file), 0);
+}