[libc-commits] [libc] [libc]: Clean up unnecessary function pointers in scanf (PR #121215)

[Vinay Deshmukh via libc-commits]

================
@@ -8,11 +8,71 @@
 
 #include "src/stdio/scanf_core/reader.h"
 #include "src/__support/macros/config.h"
+
 #include <stddef.h>
 
+#include "src/__support/File/file.h"
+#include "hdr/types/FILE.h"
+
 namespace LIBC_NAMESPACE_DECL {
 namespace scanf_core {
 
+namespace internal {
+
+#if defined(LIBC_TARGET_ARCH_IS_GPU)
+// The GPU build provides FILE access through the host operating system's
+// library. So here we simply use the public entrypoints like in the SYSTEM_FILE
+// interface. Entrypoints should normally not call others, this is an exception.
+// FIXME: We do not acquire any locks here, so this is not thread safe.
+LIBC_INLINE int getc(void *f) {
+  return LIBC_NAMESPACE::getc(reinterpret_cast<::FILE *>(f));
+}
+
+LIBC_INLINE void ungetc(int c, void *f) {
+  LIBC_NAMESPACE::ungetc(c, reinterpret_cast<::FILE *>(f));
+}
+
+#elif !defined(LIBC_COPT_STDIO_USE_SYSTEM_FILE)
+
+LIBC_INLINE int getc(void *f) {
+  unsigned char c;
+  auto result =
+      reinterpret_cast<LIBC_NAMESPACE::File *>(f)->read_unlocked(&c, 1);
+  size_t r = result.value;
+  if (result.has_error() || r != 1)
+    return '\0';
+
+  return c;
+}
+
+LIBC_INLINE void ungetc(int c, void *f) {
+  reinterpret_cast<LIBC_NAMESPACE::File *>(f)->ungetc_unlocked(c);
+}
+
+#else  // defined(LIBC_COPT_STDIO_USE_SYSTEM_FILE)
+
+// Since ungetc_unlocked isn't always available, we don't acquire the lock for
+// system files.
+LIBC_INLINE int getc(void *f) { return ::getc(reinterpret_cast<::FILE *>(f)); }
+
+LIBC_INLINE void ungetc(int c, void *f) {
+  ::ungetc(c, reinterpret_cast<::FILE *>(f));
+}
+#endif // LIBC_COPT_STDIO_USE_SYSTEM_FILE
+
+} // namespace internal
+
+char Reader::getc() {
+  ++cur_chars_read;
+  if (rb != nullptr) {
+    char output = rb->buffer[rb->buff_cur];
+    ++(rb->buff_cur);
+    return output;
+  }
+  // This should reset the buffer if applicable.
+  return static_cast<char>(internal::getc(input_stream));
+}
----------------
vinay-deshmukh wrote:

Gotcha, will move it back to header 

https://github.com/llvm/llvm-project/pull/121215