[libc] Implement more input functions on the GPU (#66288)

Summary:
This patch implements the `fgets`, `getc`, `fgetc`, and `getchar`
functions on the GPU. Their implementations are straightforward enough.
One thing worth noting is that the implementation of `fgets` will be
extremely slow due to the high latency to read a single char. A faster
solution would be to make a new RPC call to call `fgets` (due to the
special rule that newline or null breaks the stream). But this is left
out because performance isn't the primary concern here.

9 files changed, 343 insertions, 0 deletions

diff --git a/libc/src/stdio/gpu/CMakeLists.txt b/libc/src/stdio/gpu/CMakeLists.txt
index d35b1925c6a4..c47176621144 100644
--- a/libc/src/stdio/gpu/CMakeLists.txt
+++ b/libc/src/stdio/gpu/CMakeLists.txt
@@ -3,6 +3,7 @@ add_header_library(
   HDRS
     file.h
   DEPENDS
+    libc.src.__support.RPC.rpc_client
     libc.src.__support.common
     .stdin
     .stdout
@@ -10,6 +11,39 @@ add_header_library(
 )
 
 add_entrypoint_object(
+  feof
+  SRCS
+    feof.cpp
+  HDRS
+    ../feof.h
+  DEPENDS
+    libc.include.stdio
+    libc.src.__support.RPC.rpc_client
+)
+
+add_entrypoint_object(
+  ferror
+  SRCS
+    ferror.cpp
+  HDRS
+    ../ferror.h
+  DEPENDS
+    libc.include.stdio
+    libc.src.__support.RPC.rpc_client
+)
+
+add_entrypoint_object(
+  clearerr
+  SRCS
+    clearerr.cpp
+  HDRS
+    ../clearerr.h
+  DEPENDS
+    libc.include.stdio
+    libc.src.__support.RPC.rpc_client
+)
+
+add_entrypoint_object(
   fopen
   SRCS
     fopen.cpp
@@ -106,6 +140,85 @@ add_entrypoint_object(
 )
 
 add_entrypoint_object(
+  fgetc
+  SRCS
+    fgetc.cpp
+  HDRS
+    ../fgetc.h
+  DEPENDS
+    libc.include.stdio
+    .gpu_file
+)
+
+add_entrypoint_object(
+  fgetc_unlocked
+  SRCS
+    fgetc_unlocked.cpp
+  HDRS
+    ../fgetc_unlocked.h
+  DEPENDS
+    libc.include.stdio
+    .gpu_file
+)
+
+add_entrypoint_object(
+  getc
+  SRCS
+    getc.cpp
+  HDRS
+    ../getc.h
+  DEPENDS
+    libc.include.stdio
+    .gpu_file
+)
+
+add_entrypoint_object(
+  getc_unlocked
+  SRCS
+    getc_unlocked.cpp
+  HDRS
+    ../getc_unlocked.h
+  DEPENDS
+    libc.include.stdio
+    .gpu_file
+)
+
+add_entrypoint_object(
+  getchar
+  SRCS
+    getchar.cpp
+  HDRS
+    ../getchar.h
+  DEPENDS
+    libc.include.stdio
+    .gpu_file
+)
+
+add_entrypoint_object(
+  getchar_unlocked
+  SRCS
+    getc_unlocked.cpp
+  HDRS
+    ../getc_unlocked.h
+  DEPENDS
+    libc.include.stdio
+    .gpu_file
+)
+
+add_entrypoint_object(
+  fgets
+  SRCS
+    fgets.cpp
+  HDRS
+    ../fgets.h
+  DEPENDS
+    libc.include.stdio
+    .gpu_file
+    .feof
+    .ferror
+)
+
+add_entrypoint_object(
   stdin
   SRCS
     stdin.cpp
diff --git a/libc/src/stdio/gpu/clearerr.cpp b/libc/src/stdio/gpu/clearerr.cpp
new file mode 100644
index 000000000000..dc7a3729aa78
--- /dev/null
+++ b/libc/src/stdio/gpu/clearerr.cpp
@@ -0,0 +1,24 @@
+//===-- Implementation of clearerr ----------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdio/clearerr.h"
+#include "file.h"
+
+#include <stdio.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(void, clearerr, (::FILE * stream)) {
+  rpc::Client::Port port = rpc::client.open<RPC_FERROR>();
+  port.send_and_recv(
+      [=](rpc::Buffer *buffer) { buffer->data[0] = file::from_stream(stream); },
+      [&](rpc::Buffer *) {});
+  port.close();
+}
+
+} // namespace __llvm_libc
diff --git a/libc/src/stdio/gpu/feof.cpp b/libc/src/stdio/gpu/feof.cpp
new file mode 100644
index 000000000000..27d27a445812
--- /dev/null
+++ b/libc/src/stdio/gpu/feof.cpp
@@ -0,0 +1,26 @@
+//===-- Implementation of feof --------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdio/feof.h"
+#include "file.h"
+
+#include <stdio.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, feof, (::FILE * stream)) {
+  int ret;
+  rpc::Client::Port port = rpc::client.open<RPC_FEOF>();
+  port.send_and_recv(
+      [=](rpc::Buffer *buffer) { buffer->data[0] = file::from_stream(stream); },
+      [&](rpc::Buffer *buffer) { ret = static_cast<int>(buffer->data[0]); });
+  port.close();
+  return ret;
+}
+
+} // namespace __llvm_libc
diff --git a/libc/src/stdio/gpu/ferror.cpp b/libc/src/stdio/gpu/ferror.cpp
new file mode 100644
index 000000000000..e4bd631f392d
--- /dev/null
+++ b/libc/src/stdio/gpu/ferror.cpp
@@ -0,0 +1,26 @@
+//===-- Implementation of ferror ------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdio/ferror.h"
+#include "file.h"
+
+#include <stdio.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, ferror, (::FILE * stream)) {
+  int ret;
+  rpc::Client::Port port = rpc::client.open<RPC_FERROR>();
+  port.send_and_recv(
+      [=](rpc::Buffer *buffer) { buffer->data[0] = file::from_stream(stream); },
+      [&](rpc::Buffer *buffer) { ret = static_cast<int>(buffer->data[0]); });
+  port.close();
+  return ret;
+}
+
+} // namespace __llvm_libc
diff --git a/libc/src/stdio/gpu/fgetc.cpp b/libc/src/stdio/gpu/fgetc.cpp
new file mode 100644
index 000000000000..ff4ef27ccb88
--- /dev/null
+++ b/libc/src/stdio/gpu/fgetc.cpp
@@ -0,0 +1,25 @@
+//===-- GPU implementation of fgetc ---------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdio/fgetc.h"
+#include "file.h"
+
+#include <stdio.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, fgetc, (::FILE * stream)) {
+  unsigned char c;
+  size_t r = file::read(stream, &c, 1);
+
+  if (r != 1)
+    return EOF;
+  return c;
+}
+
+} // namespace __llvm_libc
diff --git a/libc/src/stdio/gpu/fgets.cpp b/libc/src/stdio/gpu/fgets.cpp
new file mode 100644
index 000000000000..df00451e2a97
--- /dev/null
+++ b/libc/src/stdio/gpu/fgets.cpp
@@ -0,0 +1,46 @@
+//===-- GPU implementation of fgets ---------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdio/fgets.h"
+#include "file.h"
+#include "src/stdio/feof.h"
+#include "src/stdio/ferror.h"
+
+#include <stddef.h>
+#include <stdio.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(char *, fgets,
+                   (char *__restrict str, int count,
+                    ::FILE *__restrict stream)) {
+  if (count < 1)
+    return nullptr;
+
+  // This implementation is very slow as it makes multiple RPC calls.
+  unsigned char c = '\0';
+  int i = 0;
+  for (; i < count - 1 && c != '\n'; ++i) {
+    auto r = file::read(stream, &c, 1);
+    if (r != 1)
+      break;
+
+    str[i] = c;
+  }
+
+  bool has_error = __llvm_libc::ferror(stream);
+  bool has_eof = __llvm_libc::feof(stream);
+
+  if (has_error || (i == 0 && has_eof))
+    return nullptr;
+
+  str[i] = '\0';
+  return str;
+}
+
+} // namespace __llvm_libc
diff --git a/libc/src/stdio/gpu/file.h b/libc/src/stdio/gpu/file.h
index 77817e070680..42395a6d4287 100644
--- a/libc/src/stdio/gpu/file.h
+++ b/libc/src/stdio/gpu/file.h
@@ -65,5 +65,38 @@ LIBC_INLINE uint64_t read(::FILE *f, void *data, size_t size) {
     return read_from_stream<RPC_READ_FROM_STREAM>(f, data, size);
 }
 
+enum Stream {
+  File = 0,
+  Stdin = 1,
+  Stdout = 2,
+  Stderr = 3,
+};
+
+// When copying between the client and server we need to indicate if this is one
+// of the special streams. We do this by enocding the low order bits of the
+// pointer to indicate if we need to use the host's standard stream.
+LIBC_INLINE uintptr_t from_stream(::FILE *f) {
+  if (f == stdin)
+    return reinterpret_cast<uintptr_t>(f) | Stdin;
+  if (f == stdout)
+    return reinterpret_cast<uintptr_t>(f) | Stdout;
+  if (f == stderr)
+    return reinterpret_cast<uintptr_t>(f) | Stderr;
+  return reinterpret_cast<uintptr_t>(f);
+}
+
+// Get the associated stream out of an encoded number.
+LIBC_INLINE ::FILE *to_stream(uintptr_t f) {
+  ::FILE *stream = reinterpret_cast<FILE *>(f & ~0x3ull);
+  Stream type = static_cast<Stream>(f & 0x3ull);
+  if (type == Stdin)
+    return stdin;
+  if (type == Stdout)
+    return stdout;
+  if (type == Stderr)
+    return stderr;
+  return stream;
+}
+
 } // namespace file
 } // namespace __llvm_libc
diff --git a/libc/src/stdio/gpu/getc.cpp b/libc/src/stdio/gpu/getc.cpp
new file mode 100644
index 000000000000..a2272221d6b7
--- /dev/null
+++ b/libc/src/stdio/gpu/getc.cpp
@@ -0,0 +1,25 @@
+//===-- GPU implementation of getc ----------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdio/getc.h"
+#include "file.h"
+
+#include <stdio.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, getc, (::FILE * stream)) {
+  unsigned char c;
+  size_t r = file::read(stream, &c, 1);
+
+  if (r != 1)
+    return EOF;
+  return c;
+}
+
+} // namespace __llvm_libc
diff --git a/libc/src/stdio/gpu/getchar.cpp b/libc/src/stdio/gpu/getchar.cpp
new file mode 100644
index 000000000000..a7a6e6c55c13
--- /dev/null
+++ b/libc/src/stdio/gpu/getchar.cpp
@@ -0,0 +1,25 @@
+//===-- GPU implementation of getchar -------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdio/getchar.h"
+#include "file.h"
+
+#include <stdio.h>
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, getchar, ()) {
+  unsigned char c;
+  size_t r = file::read(stdin, &c, 1);
+
+  if (r != 1)
+    return EOF;
+  return c;
+}
+
+} // namespace __llvm_libc