[k2] add fgets (#1519)

Author: denisichh

builtin-functions/kphp-light/stdlib/file-functions.txt

@@ -49,6 +49,8 @@ function file ($name ::: string) ::: string[] | false;
 
 function is_file ($name ::: string) ::: bool;
 
+function fgets ($stream ::: mixed, $length ::: int = -1) ::: string | false;
+
 // === UNSUPPORTED ===
 /** @kphp-extern-func-info stub generation-required */
 function chmod ($name ::: string, $mode ::: int) ::: bool;
@@ -92,8 +94,6 @@ function fgetc ($stream ::: mixed) ::: string | false;
  /** @kphp-extern-func-info stub generation-required */
 function fpassthru ($stream ::: mixed) ::: int | false;
  /** @kphp-extern-func-info stub generation-required */
-function fgets ($stream ::: mixed, $length ::: int = -1) ::: string | false;
- /** @kphp-extern-func-info stub generation-required */
 function feof ($stream ::: mixed) ::: bool;
 
 /** @kphp-extern-func-info stub generation-required */

runtime-light/k2-platform/k2-api.h

@@ -216,6 +216,10 @@ inline size_t pread(k2::descriptor descriptor, std::span<std::byte> buffer, uint
   return k2_pread(descriptor, buffer.size(), static_cast<void*>(buffer.data()), offset);
 }
 
+inline size_t fgets(k2::descriptor descriptor, std::span<std::byte> buffer) noexcept {
+  return k2_fgets(descriptor, buffer.size(), static_cast<void*>(buffer.data()));
+}
+
 inline void* mmap(k2::descriptor* md, void* addr, size_t length, int32_t prot, int32_t flags, k2::descriptor fd, uint64_t offset) noexcept {
   return k2_mmap(md, addr, length, prot, flags, fd, offset);
 }

runtime-light/k2-platform/k2-header.h

@@ -356,6 +356,13 @@ size_t k2_read(uint64_t stream_d, size_t buf_len, void* buf);
  */
 size_t k2_pread(uint64_t stream_d, size_t buf_len, void* buf, uint64_t offset);
 
+/**
+ * equivalent to libc's `fgets` function
+ *
+ * @return `0` if EOF is reached or an error occurs. total number of bytes read otherwise
+ */
+size_t k2_fgets(uint64_t stream_d, size_t buf_len, void* buf);
+
 /**
  * Semantically equivalent to libc's `mmap` function.
  *

runtime-light/stdlib/file/file-system-functions.cpp

@@ -389,3 +389,40 @@ mixed f$getimagesize(const string& name) noexcept {
 
   return result;
 }
+
+// don't forget to add "interruptible" to file-functions.txt when this function becomes a coroutine
+Optional<string> f$fgets(const resource& stream, int64_t length) noexcept {
+  if (length == 0) {
+    return false;
+  }
+
+  auto file_resource{from_mixed<class_instance<kphp::fs::file>>(stream, {})};
+  if (file_resource.is_null()) {
+    return false;
+  }
+  kphp::log::assertion(file_resource.get() != nullptr);
+  const kphp::fs::file& file{*file_resource.get()};
+
+  if (length < 0) {
+    struct stat st {};
+    kphp::log::assertion(k2::fstat(file.descriptor(), std::addressof(st)).has_value());
+    if (st.st_size <= 0) {
+      return false;
+    }
+    length = st.st_size + 1;
+  }
+
+  if (length > string::max_size()) {
+    kphp::log::warning("parameter length in function fgets mustn't be greater than string::max_size(). length = {}, string::max_size() = {}", length,
+                       string::max_size());
+    return false;
+  }
+  string res{static_cast<string::size_type>(length), false};
+  auto read_res{k2::fgets(file.descriptor(), std::as_writable_bytes(std::span<char>{res.buffer(), res.size()}))};
+
+  if (read_res == 0) {
+    return false;
+  }
+  res.shrink(static_cast<string::size_type>(read_res));
+  return res;
+}

runtime-light/stdlib/file/file-system-functions.h

@@ -274,3 +274,6 @@ inline Optional<int64_t> f$file_put_contents(const string& stream, const mixed&
 }
 
 mixed f$getimagesize(const string& name) noexcept;
+
+// don't forget to add "interruptible" to file-functions.txt when this function becomes a coroutine
+Optional<string> f$fgets(const resource& stream, int64_t length = -1) noexcept;

runtime-light/stdlib/file/resource.h

@@ -93,6 +93,8 @@ class file : public sync_resource {
 
   static auto open(std::string_view path, std::string_view mode) noexcept -> std::expected<file, int32_t>;
 
+  auto descriptor() const noexcept -> k2::descriptor;
+
   auto write(std::span<const std::byte> buf) noexcept -> std::expected<size_t, int32_t> override;
   auto read(std::span<std::byte> buf) noexcept -> std::expected<size_t, int32_t> override;
   auto pread(std::span<std::byte> buf, uint64_t offset) noexcept -> std::expected<size_t, int32_t> override;
@@ -110,6 +112,10 @@ inline auto file::open(std::string_view path, std::string_view mode) noexcept ->
   return {file{descriptor}};
 }
 
+inline auto file::descriptor() const noexcept -> k2::descriptor {
+  return m_descriptor;
+}
+
 inline auto file::write(std::span<const std::byte> buf) noexcept -> std::expected<size_t, int32_t> {
   if (m_descriptor == k2::INVALID_PLATFORM_DESCRIPTOR) [[unlikely]] {
     return std::unexpected{k2::errno_enodev};

tests/phpt/dl/473_fgets.php

@@ -0,0 +1,84 @@
+@ok
+<?php
+function init() {
+    $stream = fopen(__DIR__.'/fgets.txt', 'w');
+    fwrite ($stream, "123\n");
+    fwrite ($stream, "gucci\n");
+    fwrite ($stream, "\n");
+    fwrite ($stream, "php < kphp\n");
+    fwrite ($stream, "bang");
+    fclose ($stream);
+}
+
+function test_fgets() {
+    $stream = fopen(__DIR__ . '/fgets.txt', 'r');
+
+    var_dump (fgets ($stream)); // line = "123\n"
+
+    var_dump (fgets ($stream, 100)); // `length` greater than length of the line. line = "gucci\n"
+
+    var_dump (fgets ($stream)); // line = "\n"
+
+    var_dump (fgets ($stream, 4)); // `length` less than length of the line. line = "php < kphp\n"
+    var_dump (fgets ($stream, 1)); // always false
+    var_dump (fgets ($stream)); // rest of the line
+
+    var_dump (fgets ($stream)); // last line. line = "bang"
+
+    var_dump (fgets ($stream)); // eof
+    var_dump (fgets ($stream)); // eof
+
+    fclose($stream);
+}
+
+function test_fgets_edge_cases() {
+    $stream = fopen(__DIR__ . '/fgets.txt', 'r');
+
+    var_dump (fgets ($stream, 4)); // `length` = line.len() (without '\n'). line = "123\n"
+    var_dump (fgets ($stream)); // rest of the line
+
+    var_dump (fgets ($stream, 7)); // `length` = line.len() + 1 (with '\n'). line = "gucci\n"
+
+    // skip all lines except the last one
+    var_dump (fgets ($stream));
+    var_dump (fgets ($stream));
+
+    var_dump (fgets ($stream, 4)); // last line with `length` = line.len(). line = "bang"
+
+    fclose($stream);
+}
+
+function test_fgets_edge_case2() {
+    $stream = fopen(__DIR__ . '/fgets.txt', 'r');
+
+    // skip all lines except the last one
+    var_dump (fgets ($stream));
+    var_dump (fgets ($stream));
+    var_dump (fgets ($stream));
+    var_dump (fgets ($stream));
+
+    var_dump (fgets ($stream, 5)); // last line with `length` = line.len() + 1. line = "bang"
+
+    fclose($stream);
+}
+
+function test_fgets_mixed() {
+    $stream = fopen(__DIR__ . '/fgets.txt', 'r+');
+
+    var_dump (fgets ($stream)); // 123\n
+    var_dump (fread ($stream, 3)); // guc
+    var_dump (fgets ($stream)); // ci\n
+    var_dump (fwrite ($stream, "new string")); // \nphp < kphp\n -> new stringp\n
+    var_dump (fgets ($stream)); // p\n
+    var_dump (fread ($stream, 2)); // ba
+    var_dump (fwrite ($stream, "new string 2")); // ng -> new string 2
+    var_dump (fgets ($stream)); // eof
+
+    fclose($stream);
+}
+
+init();
+test_fgets();
+test_fgets_edge_cases();
+test_fgets_edge_case2();
+test_fgets_mixed();