fileio,main: Do not restart syscall at EAGAIN when reading for -s

src/nvim/getchar.c

@@ -2375,7 +2375,7 @@ inchar (
   // Get a character from a script file if there is one.
   // If interrupted: Stop reading script files, close them all.
   ptrdiff_t read_size = -1;
-  while (scriptin[curscript] != NULL && read_size < 0 && !ignore_script) {
+  while (scriptin[curscript] != NULL && read_size <= 0 && !ignore_script) {
     char script_char;
     if (got_int
         || (read_size = file_read(scriptin[curscript], &script_char, 1)) != 1) {
@@ -2397,7 +2397,7 @@ inchar (
     }
   }
 
-  if (read_size < 0) {  // Did not get a character from script.
+  if (read_size <= 0) {  // Did not get a character from script.
     // If we got an interrupt, skip all previously typed characters and
     // return TRUE if quit reading script file.
     // Stop reading typeahead when a single CTRL-C was read,

src/nvim/main.c

@@ -1060,11 +1060,11 @@ scripterror:
             if (STRCMP(argv[0], "-") == 0) {
               const int stdin_dup_fd = os_dup(OS_STDIN_FILENO);
               FileDescriptor *const stdin_dup = file_open_fd_new(
-                  &error, stdin_dup_fd, false, 0);
+                  &error, stdin_dup_fd, kFileReadOnly|kFileNonBlocking, 0);
               assert(stdin_dup != NULL);
               scriptin[0] = stdin_dup;
             } else if ((scriptin[0] = file_open_new(
-                &error, argv[0], kFileReadOnly, 0)) == NULL) {
+                &error, argv[0], kFileReadOnly|kFileNonBlocking, 0)) == NULL) {
               mch_errmsg(_("Cannot open for reading: \""));
               mch_errmsg(argv[0]);
               mch_errmsg("\": ");

src/nvim/os/fileio.c

@@ -74,7 +74,7 @@ int file_open(FileDescriptor *const ret_fp, const char *const fname,
   if (fd < 0) {
     return fd;
   }
-  return file_open_fd(ret_fp, fd, (wr == kTrue), mode);
+  return file_open_fd(ret_fp, fd, flags, mode);
 }
 
 /// Wrap file descriptor with FileDescriptor structure
@@ -85,17 +85,24 @@ int file_open(FileDescriptor *const ret_fp, const char *const fname,
 /// @param[out]  ret_fp  Address where information needed for reading from or
 ///                      writing to a file is saved
 /// @param[in]  fd  File descriptor to wrap.
-/// @param[in]  wr  True if fd is opened for writing only, false if it is read
+/// @param[in]  flags  Flags, @see FileOpenFlags. Currently reading from and
-///                 only.
+///                    writing to the file at once is not supported, so either
+///                    FILE_WRITE_ONLY or FILE_READ_ONLY is required.
 /// @param[in]  mode  Permissions for the newly created file (ignored if flags
 ///                   does not have FILE_CREATE\*).
 ///
 /// @return Error code (@see os_strerror()) or 0. Currently always returns 0.
 int file_open_fd(FileDescriptor *const ret_fp, const int fd,
-                 const bool wr, const int mode)
+                 const int flags, const int mode)
   FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT
 {
-  ret_fp->wr = wr;
+  ret_fp->wr = !!(flags & (kFileCreate|kFileCreateOnly
+                           |kFileTruncate
+                           |kFileAppend
+                           |kFileWriteOnly));
+  ret_fp->non_blocking = !!(flags & kFileNonBlocking);
+  // Non-blocking writes not supported currently.
+  assert(!ret_fp->wr || !ret_fp->non_blocking);
   ret_fp->fd = fd;
   ret_fp->eof = false;
   ret_fp->rv = rbuffer_new(kRWBufferSize);
@@ -134,18 +141,17 @@ FileDescriptor *file_open_new(int *const error, const char *const fname,
 /// @param[out]  error  Error code, @see os_strerror(). Is set to zero on
 ///                     success.
 /// @param[in]  fd  File descriptor to wrap.
-/// @param[in]  wr  True if fd is opened for writing only, false if it is read
+/// @param[in]  flags  Flags, @see FileOpenFlags.
-///                 only.
 /// @param[in]  mode  Permissions for the newly created file (ignored if flags
 ///                   does not have FILE_CREATE\*).
 ///
 /// @return [allocated] Opened file or NULL in case of error.
 FileDescriptor *file_open_fd_new(int *const error, const int fd,
-                                 const bool wr, const int mode)
+                                 const int flags, const int mode)
   FUNC_ATTR_NONNULL_ALL FUNC_ATTR_MALLOC FUNC_ATTR_WARN_UNUSED_RESULT
 {
   FileDescriptor *const fp = xmalloc(sizeof(*fp));
-  if ((*error = file_open_fd(fp, fd, wr, mode)) != 0) {
+  if ((*error = file_open_fd(fp, fd, flags, mode)) != 0) {
     xfree(fp);
     return NULL;
   }
@@ -224,7 +230,8 @@ static void file_rb_write_full_cb(RBuffer *const rv, FileDescriptor *const fp)
     return;
   }
   const size_t read_bytes = rbuffer_read(rv, writebuf, kRWBufferSize);
-  const ptrdiff_t wres = os_write(fp->fd, writebuf, read_bytes);
+  const ptrdiff_t wres = os_write(fp->fd, writebuf, read_bytes,
+                                  fp->non_blocking);
   if (wres != (ptrdiff_t)read_bytes) {
     if (wres >= 0) {
       fp->_error = UV_EIO;
@@ -274,7 +281,7 @@ ptrdiff_t file_read(FileDescriptor *const fp, char *const ret_buf,
       };
       assert(write_count == kRWBufferSize);
       const ptrdiff_t r_ret = os_readv(fp->fd, &fp->eof, iov,
-                                       ARRAY_SIZE(iov));
+                                       ARRAY_SIZE(iov), fp->non_blocking);
       if (r_ret > 0) {
         if (r_ret > (ptrdiff_t)read_remaining) {
           rbuffer_produced(rv, (size_t)(r_ret - (ptrdiff_t)read_remaining));
@@ -290,7 +297,8 @@ ptrdiff_t file_read(FileDescriptor *const fp, char *const ret_buf,
       if (read_remaining >= kRWBufferSize) {
         // …otherwise leave RBuffer empty and populate only target buffer,
         // because filtering information through rbuffer will be more syscalls.
-        const ptrdiff_t r_ret = os_read(fp->fd, &fp->eof, buf, read_remaining);
+        const ptrdiff_t r_ret = os_read(fp->fd, &fp->eof, buf, read_remaining,
+                                        fp->non_blocking);
         if (r_ret >= 0) {
           read_remaining -= (size_t)r_ret;
           return (ptrdiff_t)(size - read_remaining);
@@ -301,7 +309,7 @@ ptrdiff_t file_read(FileDescriptor *const fp, char *const ret_buf,
         size_t write_count;
         const ptrdiff_t r_ret = os_read(fp->fd, &fp->eof,
                                         rbuffer_write_ptr(rv, &write_count),
-                                        kRWBufferSize);
+                                        kRWBufferSize, fp->non_blocking);
         assert(write_count == kRWBufferSize);
         if (r_ret > 0) {
           rbuffer_produced(rv, (size_t)r_ret);
@@ -311,6 +319,10 @@ ptrdiff_t file_read(FileDescriptor *const fp, char *const ret_buf,
       }
 #endif
     }
+    if (fp->non_blocking) {
+      // Allow only at most one os_read[v] call.
+      break;
+    }
   }
   return (ptrdiff_t)(size - read_remaining);
 }

src/nvim/os/fileio.h

@@ -14,6 +14,7 @@ typedef struct {
   RBuffer *rv;  ///< Read or write buffer.
   bool wr;  ///< True if file is in write mode.
   bool eof;  ///< True if end of file was encountered.
+  bool non_blocking;  ///< True if EAGAIN should not restart syscalls.
 } FileDescriptor;
 
 /// file_open() flags
@@ -32,6 +33,8 @@ typedef enum {
                        ///< kFileCreateOnly.
   kFileAppend = 64,  ///< Append to the file. Implies kFileWriteOnly. Cannot
                      ///< be used with kFileCreateOnly.
+  kFileNonBlocking = 128,  ///< Do not restart read() or write() syscall if
+                           ///< EAGAIN was encountered.
 } FileOpenFlags;
 
 static inline bool file_eof(const FileDescriptor *const fp)

src/nvim/os/fs.c

@@ -462,10 +462,11 @@ os_dup_dup:
 ///                       to false. Initial value is ignored.
 /// @param[out]  ret_buf  Buffer to write to. May be NULL if size is zero.
 /// @param[in]  size  Amount of bytes to read.
+/// @param[in]  non_blocking  Do not restart syscall if EAGAIN was encountered.
 ///
 /// @return Number of bytes read or libuv error code (< 0).
-ptrdiff_t os_read(const int fd, bool *ret_eof, char *const ret_buf,
+ptrdiff_t os_read(const int fd, bool *const ret_eof, char *const ret_buf,
-                  const size_t size)
+                  const size_t size, const bool non_blocking)
   FUNC_ATTR_WARN_UNUSED_RESULT
 {
   *ret_eof = false;
@@ -485,7 +486,9 @@ ptrdiff_t os_read(const int fd, bool *ret_eof, char *const ret_buf,
     if (cur_read_bytes < 0) {
       const int error = os_translate_sys_error(errno);
       errno = 0;
-      if (error == UV_EINTR || error == UV_EAGAIN) {
+      if (non_blocking && error == UV_EAGAIN) {
+        break;
+      } else if (error == UV_EINTR || error == UV_EAGAIN) {
         continue;
       } else if (error == UV_ENOMEM && !did_try_to_free) {
         try_to_free_memory();
@@ -515,7 +518,11 @@ ptrdiff_t os_read(const int fd, bool *ret_eof, char *const ret_buf,
 ///                   may change, it is incorrect to use data it points to after
 ///                   os_readv().
 /// @param[in]  iov_size  Number of buffers in iov.
-ptrdiff_t os_readv(int fd, bool *ret_eof, struct iovec *iov, size_t iov_size)
+/// @param[in]  non_blocking  Do not restart syscall if EAGAIN was encountered.
+///
+/// @return Number of bytes read or libuv error code (< 0).
+ptrdiff_t os_readv(const int fd, bool *const ret_eof, struct iovec *iov,
+                   size_t iov_size, const bool non_blocking)
   FUNC_ATTR_NONNULL_ALL
 {
   *ret_eof = false;
@@ -548,7 +555,9 @@ ptrdiff_t os_readv(int fd, bool *ret_eof, struct iovec *iov, size_t iov_size)
     } else if (cur_read_bytes < 0) {
       const int error = os_translate_sys_error(errno);
       errno = 0;
-      if (error == UV_EINTR || error == UV_EAGAIN) {
+      if (non_blocking && error == UV_EAGAIN) {
+        break;
+      } else if (error == UV_EINTR || error == UV_EAGAIN) {
         continue;
       } else if (error == UV_ENOMEM && !did_try_to_free) {
         try_to_free_memory();
@@ -568,9 +577,11 @@ ptrdiff_t os_readv(int fd, bool *ret_eof, struct iovec *iov, size_t iov_size)
 /// @param[in]  fd  File descriptor to write to.
 /// @param[in]  buf  Data to write. May be NULL if size is zero.
 /// @param[in]  size  Amount of bytes to write.
+/// @param[in]  non_blocking  Do not restart syscall if EAGAIN was encountered.
 ///
 /// @return Number of bytes written or libuv error code (< 0).
-ptrdiff_t os_write(const int fd, const char *const buf, const size_t size)
+ptrdiff_t os_write(const int fd, const char *const buf, const size_t size,
+                   const bool non_blocking)
   FUNC_ATTR_WARN_UNUSED_RESULT
 {
   if (buf == NULL) {
@@ -588,7 +599,9 @@ ptrdiff_t os_write(const int fd, const char *const buf, const size_t size)
     if (cur_written_bytes < 0) {
       const int error = os_translate_sys_error(errno);
       errno = 0;
-      if (error == UV_EINTR || error == UV_EAGAIN) {
+      if (non_blocking && error == UV_EAGAIN) {
+        break;
+      } else if (error == UV_EINTR || error == UV_EAGAIN) {
         continue;
       } else {
         return error;

test/unit/os/fs_spec.lua

@@ -382,7 +382,7 @@ describe('fs function', function()
         buf = ffi.new('char[?]', size + 1, ('\0'):rep(size))
       end
       local eof = ffi.new('bool[?]', 1, {true})
-      local ret2 = fs.os_read(fd, eof, buf, size)
+      local ret2 = fs.os_read(fd, eof, buf, size, false)
       local ret1 = eof[0]
       local ret3 = ''
       if buf ~= nil then
@@ -400,7 +400,7 @@ describe('fs function', function()
       end
       local iov = ffi.new('struct iovec[?]', #sizes, bufs)
       local eof = ffi.new('bool[?]', 1, {true})
-      local ret2 = fs.os_readv(fd, eof, iov, #sizes)
+      local ret2 = fs.os_readv(fd, eof, iov, #sizes, false)
       local ret1 = eof[0]
       local ret3 = {}
       for i = 1,#sizes do
@@ -410,7 +410,7 @@ describe('fs function', function()
       return ret1, ret2, ret3
     end
     local function os_write(fd, data)
-      return fs.os_write(fd, data, data and #data or 0)
+      return fs.os_write(fd, data, data and #data or 0, false)
     end
 
     describe('os_path_exists', function()