More work on pager kitten

kittens/pager/file_input.go

@@ -0,0 +1,71 @@
+// License: GPLv3 Copyright: 2024, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package pager
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"golang.org/x/sys/unix"
+)
+
+var _ = fmt.Print
+
+func read_input(input_file *os.File, input_file_name string, input_channel chan<- input_line_struct) {
+	const buf_capacity = 8192
+	var buf_array [buf_capacity]byte
+	output_buf := strings.Builder{}
+	output_buf.Grow(buf_capacity)
+	var err error
+	var n int
+
+	defer func() {
+		_ = input_file.Close()
+		last := input_line_struct{line: output_buf.String(), err: err}
+		if errors.Is(err, io.EOF) {
+			last.err = nil
+		}
+		if len(last.line) > 0 || last.err != nil {
+			input_channel <- last
+		}
+		close(input_channel)
+	}()
+
+	process_chunk := func(chunk []byte) {
+		for len(chunk) > 0 {
+			idx := bytes.IndexByte(chunk, '\n')
+			switch idx {
+			case -1:
+				_, _ = output_buf.Write(chunk)
+				chunk = nil
+			default:
+				_, _ = output_buf.Write(chunk[idx:])
+				chunk = chunk[idx+1:]
+				input_channel <- input_line_struct{line: output_buf.String()}
+				output_buf.Reset()
+				output_buf.Grow(buf_capacity)
+			}
+		}
+	}
+
+	read_with_retry := func(b []byte) (n int, err error) {
+		for {
+			n, err = input_file.Read(b)
+			if err != unix.EAGAIN && err != unix.EINTR {
+				break
+			}
+		}
+		return
+	}
+
+	for err != nil {
+		n, err = read_with_retry(buf_array[:])
+		if n > 0 {
+			process_chunk(buf_array[:n])
+		}
+	}
+}

kittens/pager/main.go

@@ -14,6 +14,7 @@ package pager
 
 import (
 	"fmt"
+	"os"
 
 	"kitty/tools/cli"
 	"kitty/tools/tty"
@@ -23,7 +24,42 @@ var _ = fmt.Print
 var debugprintln = tty.DebugPrintln
 var _ = debugprintln
 
+type input_line_struct struct {
+	line string
+	err  error
+}
+
+type global_state_struct struct {
+	input_file_name string
+	opts            *Options
+}
+
+var global_state global_state_struct
+
 func main(_ *cli.Command, opts_ *Options, args []string) (rc int, err error) {
+	global_state.opts = opts_
+	input_channel := make(chan input_line_struct, 4096)
+	var input_file *os.File
+	if len(args) > 1 {
+		return 1, fmt.Errorf("Only a single file can be viewed at a time")
+	}
+	if len(args) == 0 {
+		if tty.IsTerminal(os.Stdin.Fd()) {
+			return 1, fmt.Errorf("STDIN is a terminal and no filename specified. See --help")
+		}
+		input_file = os.Stdin
+		global_state.input_file_name = "/dev/stdin"
+	} else {
+		input_file, err = os.Open(args[0])
+		if err != nil {
+			return 1, err
+		}
+		if tty.IsTerminal(input_file.Fd()) {
+			return 1, fmt.Errorf("%s is a terminal not paging it", args[0])
+		}
+		global_state.input_file_name = args[0]
+	}
+	go read_input(input_file, global_state.input_file_name, input_channel)
 	return
 }
 

kittens/pager/main.py

@@ -14,7 +14,11 @@ choices=pager,scrollback
 The role the pager is used for. The default is a standard less like pager.
 '''.format
 
-help_text = 'Display text in a pager with various features such as searching, copy/paste, etc. Text can some from the specified file or from STDIN.'
+help_text = '''\
+Display text in a pager with various features such as searching, copy/paste, etc.
+Text can some from the specified file or from STDIN. If no filename is specified
+and STDIN is not a TTY, it is used.
+'''
 usage = '[filename]'