[k2] add file_exists (#1465)

Author: astrophysik

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

@@ -38,6 +38,8 @@ function sprintf ($format ::: string, ...$args) ::: string;
 
 function vsprintf ($format ::: string, $args ::: array) ::: string;
 
+function file_exists ($name ::: string) ::: bool;
+
 // === UNSUPPORTED ===
 
 /** @kphp-extern-func-info stub generation-required */
@@ -51,8 +53,6 @@ function file ($name ::: string) ::: string[] | false;
 /** @kphp-extern-func-info stub generation-required */
 function file_put_contents ($name ::: string, $content ::: mixed, $flags ::: int = 0) ::: int | false;
 /** @kphp-extern-func-info stub generation-required */
-function file_exists ($name ::: string) ::: bool;
-/** @kphp-extern-func-info stub generation-required */
 function filectime ($name ::: string) ::: int | false;
 /** @kphp-extern-func-info stub generation-required */
 function filemtime ($name ::: string) ::: int | false;

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

@@ -45,6 +45,7 @@ inline constexpr int32_t errno_etimedout = ETIMEDOUT;
 inline constexpr int32_t errno_eshutdown = ESHUTDOWN;
 inline constexpr int32_t errno_ecanceled = ECANCELED;
 inline constexpr int32_t errno_erange = ERANGE;
+inline constexpr int32_t errno_enoent = ENOENT;
 
 using descriptor = uint64_t;
 inline constexpr k2::descriptor INVALID_PLATFORM_DESCRIPTOR = 0;
@@ -176,6 +177,13 @@ inline auto readdir(k2::descriptor descriptor) noexcept {
              : return_type{std::nullopt};
 }
 
+inline std::expected<void, int32_t> access(std::string_view path, int32_t mode) noexcept {
+  if (auto error_code{k2_access(path.data(), path.size(), mode)}; error_code != k2::errno_ok) [[unlikely]] {
+    return std::unexpected{error_code};
+  }
+  return {};
+}
+
 inline std::expected<void, int32_t> unlink(std::string_view path) noexcept {
   if (auto error_code{k2_unlink(path.data(), path.size())}; error_code != k2::errno_ok) [[unlikely]] {
     return std::unexpected{error_code};
@@ -184,8 +192,8 @@ inline std::expected<void, int32_t> unlink(std::string_view path) noexcept {
   }
 }
 
-inline int32_t access(std::string_view component_name) noexcept {
-  return k2_access(component_name.size(), component_name.data());
+inline int32_t component_access(std::string_view component_name) noexcept {
+  return k2_component_access(component_name.size(), component_name.data());
 }
 
 inline void stream_status(k2::descriptor descriptor, StreamStatus* status) noexcept {

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

@@ -27,7 +27,7 @@
 #include <time.h>
 #endif
 
-#define K2_PLATFORM_HEADER_H_VERSION 12
+#define K2_PLATFORM_HEADER_H_VERSION 13
 
 // Always check that enum value is a valid value!
 
@@ -280,6 +280,14 @@ struct DirEntry {
  */
 int32_t k2_readdir(uint64_t dd, struct DirEntry* entry, struct DirEntry** result);
 
+/**
+ * Semantically equivalent to libc's `access` function.
+ *
+ * @return On success (all requested permissions granted), zero is returned. On failure, returns a non-zero value corresponding to a libc-like `errno`.
+ *
+ */
+int32_t k2_access(const char* pathname, size_t pathname_len, int32_t mode);
+
 /**
  * Semantically equivalent of libc's unlink
  *
@@ -299,7 +307,7 @@ int32_t k2_unlink(const char* path, size_t path_len);
  * `EINVAL` => `name` has invalid format (empty, non ascii, too long, etc..)
  * `EACCES` => permission denied
  */
-int32_t k2_access(size_t name_len, const char* name);
+int32_t k2_component_access(size_t name_len, const char* name);
 
 /**
  * If the write or read status is `Blocked` - then the platform ensures that

runtime-light/stdlib/confdata/confdata-functions.h

@@ -11,7 +11,7 @@
 #include "runtime-light/stdlib/diagnostics/logs.h"
 
 inline bool f$is_confdata_loaded() noexcept {
-  return k2::access(kphp::confdata::COMPONENT_NAME) == k2::errno_ok;
+  return k2::component_access(kphp::confdata::COMPONENT_NAME) == k2::errno_ok;
 }
 
 // SAFETY: `key` is only used before await point

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

@@ -13,6 +13,7 @@
 #include <span>
 #include <string_view>
 #include <sys/stat.h>
+#include <unistd.h>
 #include <utility>
 
 #include "runtime-common/core/runtime-core.h"
@@ -114,6 +115,11 @@ inline kphp::coro::task<bool> f$fclose(resource stream) noexcept {
   co_return false;
 }
 
+inline bool f$file_exists(const string& name) noexcept {
+  const auto exists_res{k2::access(std::string_view{name.c_str(), name.size()}, F_OK)};
+  return exists_res.has_value();
+}
+
 inline bool f$unlink(const string& name) noexcept {
   std::expected<void, int32_t> unlink_res{k2::unlink(std::string_view{name.c_str(), name.size()})};
   return unlink_res.has_value();