Start work on the transmit backend

tools/cmd/icat/transmit.go

@@ -0,0 +1,100 @@
+// License: GPLv3 Copyright: 2022, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package icat
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"kitty/tools/tui/graphics"
+	"kitty/tools/utils/shm"
+	"os"
+)
+
+var _ = fmt.Print
+
+func gc_for_image(imgd *image_data) *graphics.GraphicsCommand {
+}
+
+func transmit_shm(imgd *image_data, frame_num int, frame *image_frame) error {
+	var data_size int
+	if frame.in_memory_bytes == nil {
+		f, err := os.Open(frame.filename)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+		sz, _ := f.Seek(0, io.SeekEnd)
+		f.Seek(0, io.SeekStart)
+		mmap, err := shm.CreateTemp("icat-*", uint64(sz))
+		if err != nil {
+			return err
+		}
+		defer mmap.Close()
+		dest := mmap.Slice()
+		for len(dest) > 0 {
+			n, err := f.Read(dest)
+			dest = dest[n:]
+			if err != nil {
+				if errors.Is(err, io.EOF) {
+					break
+				}
+				mmap.Unlink()
+				return err
+			}
+		}
+		data_size = len(mmap.Slice()) - len(dest)
+	} else {
+		mmap, err := shm.CreateTemp("icat-*", uint64(len(frame.in_memory_bytes)))
+		if err != nil {
+			return err
+		}
+		defer mmap.Close()
+		data_size = copy(mmap.Slice(), frame.in_memory_bytes)
+	}
+}
+
+func transmit_file(imgd *image_data, frame_num int, frame *image_frame) error {
+}
+
+func transmit_stream(imgd *image_data, frame_num int, frame *image_frame) error {
+}
+
+func transmit_image(imgd *image_data) {
+	defer func() {
+		for _, frame := range imgd.frames {
+			if frame.filename_is_temporary && frame.filename != "" {
+				os.Remove(frame.filename)
+				frame.filename = ""
+			}
+			frame.in_memory_bytes = nil
+		}
+	}()
+	var f func(*image_data, int, *image_frame) error
+	if opts.TransferMode != "detect" {
+		switch opts.TransferMode {
+		case "file":
+			f = transmit_file
+		case "memory":
+			f = transmit_shm
+		case "stream":
+			f = transmit_stream
+			return
+		}
+	}
+	if f == nil && transfer_by_memory == supported && imgd.frames[0].in_memory_bytes != nil {
+		f = transmit_shm
+	}
+	if f == nil && transfer_by_file == supported {
+		f = transmit_file
+	}
+	if f == nil {
+		f = transmit_stream
+	}
+	for frame_num, frame := range imgd.frames {
+		err := f(imgd, frame_num, &frame)
+		if err != nil {
+			print_error("Failed to transmit %s with error: %v", imgd.source_name, err)
+		}
+	}
+}