[libc-commits] [libc] [libc] Add getpwent, setpwent, and endpwent entrypoints (PR #213076)

[Alexey Samsonov via libc-commits]

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@@ -0,0 +1,170 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Implementation of getpwent.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/pwd/getpwent.h"
+#include "src/__support/CPP/span.h"
+#include "src/__support/File/file.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+#include "src/pwd/pwd_utils.h"
+
+#include "hdr/stdio_macros.h"
+
+#ifndef LIBC_COPT_PWD_FILE_PATH
+#define LIBC_COPT_PWD_FILE_PATH "/etc/passwd"
+#endif
+
+namespace LIBC_NAMESPACE_DECL {
+
+static File *pwd_file = nullptr;
+static const char *pwd_file_path = LIBC_COPT_PWD_FILE_PATH;
+// Note: These static buffers are process-global and NOT protected by a mutex
+// at this stage. POSIX getpwent is non-reentrant.
+static char line_buffer[1024];
+static struct passwd pwd_entry;
+
+namespace internal {
+void set_passwd_path(const char *path) {
+  if (!path)
+    return;
+  if (pwd_file) {
+    pwd_file->close();
+    pwd_file = nullptr;
+  }
+  pwd_file_path = path;
+}
+} // namespace internal
+
+ErrorOr<int> setpwent_impl() {
+  if (!pwd_file) {
+    auto result = openfile(pwd_file_path, "r");
+    if (!result.has_value())
+      return Error(result.error());
+    pwd_file = result.value();
+  } else {
+    auto result = pwd_file->seek(0, SEEK_SET);
+    if (!result.has_value())
+      return Error(result.error());
+  }
+  return 0;
+}
+
+ErrorOr<int> endpwent_impl() {
+  if (pwd_file) {
+    int result = pwd_file->close();
+    pwd_file = nullptr;
+    if (result != 0)
+      return Error(result);
+  }
+  return 0;
+}
+
+struct ReadLineResult {
+  size_t bytes_read;
+  bool truncated;
+};
+
+// Reads a line from the given file into buf.
+static ErrorOr<ReadLineResult> read_line(File *f, cpp::span<char> buf) {
+  if (!f || buf.empty())
+    return Error(EINVAL);
+
+  f->lock();
+  size_t bytes_read = 0;
+  FileIOResult result(0);
+  bool truncated = false;
+
+  for (char &ch : buf.first(buf.size() - 1)) {
+    result = f->read_unlocked(&ch, 1);
+    if (result.has_error()) {
+      f->unlock();
+      return Error(result.error);
+    }
+    if (result.value != 1)
+      break;
+    ++bytes_read;
+    if (ch == '\n')
+      break;
+  }
+
+  if (result.value == 1 && bytes_read > 0 && buf[bytes_read - 1] != '\n') {
+    truncated = true;
+    char c = '\0';
+    while (true) {
+      result = f->read_unlocked(&c, 1);
+      if (result.has_error()) {
+        f->unlock();
+        return Error(result.error);
+      }
+      if (result.value != 1 || c == '\n')
+        break;
+    }
+  }
+
+  bool has_error = f->error_unlocked();
+  bool has_eof = f->iseof_unlocked();
+  f->unlock();
+
+  if (has_error)
+    return Error(EIO);
+
+  if (bytes_read == 0 && has_eof)
+    return ReadLineResult{0, false};
+
+  buf[bytes_read] = '\0';
+  return ReadLineResult{bytes_read, truncated};
+}
+
+LLVM_LIBC_FUNCTION(struct passwd *, getpwent, ()) {
+  if (!pwd_file) {
+    auto result = openfile(pwd_file_path, "r");
+    if (!result.has_value()) {
+      libc_errno = result.error();
+      return nullptr;
+    }
+    pwd_file = result.value();
+  }
+
+  while (true) {
+    auto result = read_line(pwd_file, line_buffer);
+    if (!result.has_value()) {
+      libc_errno = result.error();
----------------
vonosmas wrote:

IMO it would be a bit cleaner to convert this whole function into ErrorOr<struct passwd*>, and set `libc_errno` in the calling entrypoint, if the error is returned.

https://github.com/llvm/llvm-project/pull/213076