[libc-commits] [libc] [libc] Add struct group header and group line parser (PR #224208)

[Michael Jones via libc-commits]

================
@@ -0,0 +1,199 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 helper functions and parser for grp.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/grp/grp_utils.h"
+#include "hdr/errno_macros.h"
+#include "hdr/stdint_proxy.h"
+#include "hdr/types/gid_t.h"
+#include "hdr/types/size_t.h"
+#include "hdr/types/struct_group.h"
+#include "src/__support/CPP/span.h"
+#include "src/__support/ctype_utils.h"
+#include "src/__support/error_or.h"
+#include "src/__support/macros/attributes.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/pwd/dynamic_buffer.h"
+#include "src/__support/pwd/field_tokenizer.h"
+#include "src/__support/pwd/flat_file_db.h"
+#include "src/__support/str_to_integer.h"
+
+#ifndef LIBC_COPT_GROUP_FILE_PATH
+#define LIBC_COPT_GROUP_FILE_PATH "/etc/group"
+#endif
+
+namespace LIBC_NAMESPACE_DECL {
+namespace {
+
+// TODO: Replace with cpp::count when available in
+// src/__support/CPP/algorithm.h.
+size_t count_group_members(cpp::span<const char> line) {
+  size_t max_members = 1;
+  for (char c : line) {
+    if (c == ',')
+      ++max_members;
+  }
+  return max_members;
+}
+
+// Parse fixed fields (name, passwd, gid).
+bool parse_group_fields(cpp::span<char> line, struct group *grp,
+                        cpp::span<char> *members_out) {
+  if (line.empty() || !grp || !members_out)
+    return false;
+
+  pwd::FieldTokenizer tokenizer(line, ':');
+
+  auto name = tokenizer.next_field();
+  if (!name || name->empty() || name->front() == '\0')
+    return false;
+  grp->gr_name = name->data();
+
+  auto passwd = tokenizer.next_field();
+  if (!passwd)
+    return false;
+  grp->gr_passwd = passwd->data();
+
+  auto gid_str = tokenizer.next_field();
+  if (!gid_str || gid_str->empty() || !internal::isdigit(gid_str->front()))
+    return false;
+  auto gid_res = internal::strtointeger<gid_t>(gid_str->data(), 10);
+  if (gid_res.has_error() || gid_res.parsed_len <= 0 ||
+      static_cast<size_t>(gid_res.parsed_len) + 1 != gid_str->size() ||
+      (*gid_str)[gid_res.parsed_len] != '\0')
+    return false;
+  grp->gr_gid = gid_res.value;
+
+  auto members_field = tokenizer.next_field();
+  if (!members_field)
+    return false;
+
+  // Trailing delimiters or fields are invalid.
+  if (tokenizer.next_field())
+    return false;
+
+  *members_out = *members_field;
+  return true;
+}
+
+} // namespace
+
+namespace pwd {
+
+template <>
+ErrorOr<void> parse_line<struct group>(cpp::span<char> line,
+                                       cpp::span<char> scratch,
+                                       struct group *grp) {
+  if (!grp || line.empty() || line.back() != '\0')
+    return Error(EINVAL);
+
+  // Line excluding terminating null byte.
+  cpp::span<char> text = line.first(line.size() - 1);
+  for (char c : text) {
+    if (c == '\0')
+      return Error(EINVAL);
+  }
+
+  size_t max_members = count_group_members(text);
+  uintptr_t tail = reinterpret_cast<uintptr_t>(scratch.data());
+  size_t pad = (alignof(char *) - tail % alignof(char *)) % alignof(char *);
----------------
michaelrj-google wrote:

maybe add a comment explaining what you're calculating here? It's a bit hard to parse. Also `pad` is never modified and could be const. Same for some of the other variables.

https://github.com/llvm/llvm-project/pull/224208