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less.cpp
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/*
* Copyright (c) 2021, Peter Elliott <pelliott@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/LexicalPath.h>
#include <LibCore/ArgsParser.h>
#include <LibCore/System.h>
#include <LibLine/Editor.h>
#include <LibMain/Main.h>
#include <csignal>
#include <stdio.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <unistd.h>
static struct termios g_save;
// Flag set by a SIGWINCH signal handler to notify the main loop that the window has been resized.
static Atomic<bool> g_resized { false };
static ErrorOr<void> setup_tty(bool switch_buffer)
{
// Save previous tty settings.
g_save = TRY(Core::System::tcgetattr(STDOUT_FILENO));
struct termios raw = g_save;
raw.c_lflag &= ~(ECHO | ICANON);
// Disable echo and line buffering
TRY(Core::System::tcsetattr(STDOUT_FILENO, TCSAFLUSH, raw));
if (switch_buffer) {
// Save cursor and switch to alternate buffer.
out("\e[s\e[?1047h");
}
return {};
}
static ErrorOr<void> teardown_tty(bool switch_buffer)
{
TRY(Core::System::tcsetattr(STDOUT_FILENO, TCSAFLUSH, g_save));
if (switch_buffer) {
out("\e[?1047l\e[u");
}
return {};
}
static Vector<StringView> wrap_line(DeprecatedString const& string, size_t width)
{
auto const result = Line::Editor::actual_rendered_string_metrics(string, {}, width);
Vector<StringView> spans;
size_t span_start = 0;
for (auto const& line_metric : result.line_metrics) {
VERIFY(line_metric.bit_length.has_value());
auto const bit_length = line_metric.bit_length.value();
spans.append(string.substring_view(span_start, bit_length));
span_start += bit_length;
}
return spans;
}
class Pager {
public:
Pager(StringView filename, FILE* file, FILE* tty, StringView prompt)
: m_file(file)
, m_tty(tty)
, m_filename(filename)
, m_prompt(prompt)
{
}
void up()
{
up_n(1);
}
void down()
{
down_n(1);
}
void up_page()
{
up_n(m_height - 1);
}
void down_page()
{
down_n(m_height - 1);
}
void up_n(size_t n)
{
if (m_line == 0 && m_subline == 0)
return;
line_subline_add(m_line, m_subline, -n);
full_redraw();
}
void down_n(size_t n)
{
if (at_end())
return;
clear_status();
read_enough_for_line(m_line + n);
size_t real_n = line_subline_add(m_line, m_subline, n);
// If we are moving less than a screen down, just draw the extra lines
// for efficiency and more(1) compatibility.
if (n < m_height - 1) {
size_t line = m_line;
size_t subline = m_subline;
line_subline_add(line, subline, (m_height - 1) - real_n, false);
write_range(line, subline, real_n);
} else {
write_range(m_line, m_subline, m_height - 1);
}
status_line();
fflush(m_tty);
}
void top()
{
m_line = 0;
m_subline = 0;
full_redraw();
}
void bottom()
{
while (read_line())
;
m_line = end_line();
m_subline = end_subline();
full_redraw();
}
void up_half_page()
{
up_n(m_height / 2);
}
void down_half_page()
{
down_n(m_height / 2);
}
void go_to_line(size_t line_num)
{
read_enough_for_line(line_num);
m_line = line_num;
m_subline = 0;
bound_cursor();
full_redraw();
}
void init()
{
resize(false);
}
void resize(bool clear = true)
{
// First, we get the current size of the window.
struct winsize window;
if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &window) == -1) {
perror("ioctl(2)");
return;
}
auto original_height = m_height;
m_width = window.ws_col;
m_height = window.ws_row;
// If the window is now larger than it was before, read more lines of
// the file so that there is enough data to fill the whole screen.
//
// m_height is initialized to 0, so if the terminal was 80x25 when
// this is called for the first time, then additional_lines will be 80
// and 80 lines of text will be buffered.
auto additional_lines = m_height - original_height;
while (additional_lines > 0) {
if (!read_line()) {
// End of file has been reached.
break;
}
--additional_lines;
}
reflow();
bound_cursor();
// Next, we repaint the whole screen. We need to figure out what line was at the top
// of the screen, and seek there and re-display everything again.
if (clear) {
full_redraw();
} else {
redraw();
}
}
size_t write_range(size_t line, size_t subline, size_t length)
{
size_t lines = 0;
for (size_t i = line; i < m_lines.size(); ++i) {
for (auto string : sublines(i)) {
if (subline > 0) {
--subline;
continue;
}
if (lines >= length)
return lines;
outln(m_tty, "{}", string);
++lines;
}
}
return lines;
}
void clear_status()
{
out(m_tty, "\e[2K\r");
}
void status_line()
{
out(m_tty, "\e[0;7m ");
render_status_line(m_prompt);
out(m_tty, " \e[0m");
}
bool read_line()
{
char* line = nullptr;
size_t n = 0;
ssize_t size = getline(&line, &n, m_file);
ScopeGuard guard([line] {
free(line);
});
if (size == -1)
return false;
// Strip trailing newline.
if (line[size - 1] == '\n')
--size;
m_lines.append(DeprecatedString(line, size));
return true;
}
bool at_end()
{
return feof(m_file) && m_line == end_line() && m_subline == end_subline();
}
private:
void redraw()
{
write_range(m_line, m_subline, m_height - 1);
status_line();
fflush(m_tty);
}
void full_redraw()
{
out("\e[2J\e[0G\e[0d");
redraw();
}
void read_enough_for_line(size_t line)
{
// This might read a bounded number of extra lines.
while (m_lines.size() < line + m_height) {
if (!read_line())
break;
}
}
size_t render_status_line(StringView prompt, size_t off = 0, char end = '\0', bool ignored = false)
{
for (; off < prompt.length() && prompt[off] != end; ++off) {
if (ignored)
continue;
if (off + 1 >= prompt.length()) {
// Don't parse any multi-character sequences if we are at the end of input.
out(m_tty, "{}", prompt[off]);
continue;
}
switch (prompt[off]) {
case '?':
switch (prompt[++off]) {
case 'f':
off = render_status_line(prompt, off + 1, ':', m_file == stdin);
off = render_status_line(prompt, off + 1, '.', m_file != stdin);
break;
case 'e':
off = render_status_line(prompt, off + 1, ':', !at_end());
off = render_status_line(prompt, off + 1, '.', at_end());
break;
default:
// Unknown flags are never true.
off = render_status_line(prompt, off + 1, ':', true);
off = render_status_line(prompt, off + 1, '.', false);
}
break;
case '%':
switch (prompt[++off]) {
case 'f':
out(m_tty, "{}", m_filename);
break;
case 'l':
out(m_tty, "{}", m_line + 1);
break;
default:
out(m_tty, "?");
}
break;
case '\\':
++off;
[[fallthrough]];
default:
out(m_tty, "{}", prompt[off]);
}
}
return off;
}
Vector<StringView> const& sublines(size_t line)
{
return m_subline_cache.ensure(line, [&]() {
return wrap_line(m_lines[line], m_width);
});
}
size_t line_subline_add(size_t& line, size_t& subline, int delta, bool bounded = true)
{
int unit = delta / AK::abs(delta);
size_t i;
for (i = 0; i < (size_t)AK::abs(delta); ++i) {
if (subline == 0 && unit == -1) {
if (line == 0)
return i;
line--;
subline = sublines(line).size() - 1;
} else if (subline == sublines(line).size() - 1 && unit == 1) {
if (bounded && feof(m_file) && line == end_line() && subline == end_subline())
return i;
if (line >= m_lines.size() - 1)
return i;
line++;
subline = 0;
} else {
subline += unit;
}
}
return i;
}
void bound_cursor()
{
if (!feof(m_file))
return;
if (m_line == end_line() && m_subline >= end_subline()) {
m_subline = end_subline();
} else if (m_line > end_line()) {
m_line = end_line();
m_subline = end_subline();
}
}
void calculate_end()
{
if (m_lines.is_empty()) {
m_end_line = 0;
m_end_subline = 0;
return;
}
size_t end_line = m_lines.size() - 1;
size_t end_subline = sublines(end_line).size() - 1;
line_subline_add(end_line, end_subline, -(m_height - 1), false);
m_end_line = end_line;
m_end_subline = end_subline;
}
// Only valid after all lines are read.
size_t end_line()
{
if (!m_end_line.has_value())
calculate_end();
return m_end_line.value();
}
// Only valid after all lines are read.
size_t end_subline()
{
if (!m_end_subline.has_value())
calculate_end();
return m_end_subline.value();
}
void reflow()
{
m_subline_cache.clear();
m_end_line = {};
m_end_subline = {};
m_subline = 0;
}
// FIXME: Don't save scrollback when emulating more.
Vector<DeprecatedString> m_lines;
size_t m_line { 0 };
size_t m_subline { 0 };
HashMap<size_t, Vector<StringView>> m_subline_cache;
Optional<size_t> m_end_line;
Optional<size_t> m_end_subline;
FILE* m_file;
FILE* m_tty;
size_t m_width { 0 };
size_t m_height { 0 };
DeprecatedString m_filename;
DeprecatedString m_prompt;
};
/// Return the next key sequence, or nothing if a signal is received while waiting
/// to read the next sequence.
static Optional<DeprecatedString> get_key_sequence()
{
// We need a buffer to handle ansi sequences.
char buff[8];
ssize_t n = read(STDOUT_FILENO, buff, sizeof(buff));
if (n > 0) {
return DeprecatedString(buff, n);
} else {
return {};
}
}
static void cat_file(FILE* file)
{
Array<u8, 4096> buffer;
while (!feof(file)) {
size_t n = fread(buffer.data(), 1, buffer.size(), file);
if (n == 0 && ferror(file)) {
perror("fread");
exit(1);
}
n = fwrite(buffer.data(), 1, n, stdout);
if (n == 0 && ferror(stdout)) {
perror("fwrite");
exit(1);
}
}
}
ErrorOr<int> serenity_main(Main::Arguments arguments)
{
TRY(Core::System::pledge("stdio rpath tty sigaction"));
// FIXME: Make these into StringViews once we stop using fopen below.
DeprecatedString filename = "-";
DeprecatedString prompt = "?f%f :.(line %l)?e (END):.";
bool dont_switch_buffer = false;
bool quit_at_eof = false;
bool emulate_more = false;
if (LexicalPath::basename(arguments.strings[0]) == "more"sv)
emulate_more = true;
Core::ArgsParser args_parser;
args_parser.add_positional_argument(filename, "The paged file", "file", Core::ArgsParser::Required::No);
args_parser.add_option(prompt, "Prompt line", "prompt", 'P', "Prompt");
args_parser.add_option(dont_switch_buffer, "Don't use xterm alternate buffer", "no-init", 'X');
args_parser.add_option(quit_at_eof, "Exit when the end of the file is reached", "quit-at-eof", 'e');
args_parser.add_option(emulate_more, "Pretend that we are more(1)", "emulate-more", 'm');
args_parser.parse(arguments);
FILE* file;
if (DeprecatedString("-") == filename) {
file = stdin;
} else if ((file = fopen(filename.characters(), "r")) == nullptr) {
perror("fopen");
exit(1);
}
// On SIGWINCH set this flag so that the main-loop knows when the terminal
// has been resized.
signal(SIGWINCH, [](auto) {
g_resized = true;
});
TRY(Core::System::pledge("stdio tty"));
if (emulate_more) {
// Configure options that match more's behavior
dont_switch_buffer = true;
quit_at_eof = true;
prompt = "--More--";
}
if (!isatty(STDOUT_FILENO)) {
cat_file(file);
return 0;
}
TRY(setup_tty(!dont_switch_buffer));
Pager pager(filename, file, stdout, prompt);
pager.init();
StringBuilder modifier_buffer = StringBuilder(10);
for (Optional<DeprecatedString> sequence_value;; sequence_value = get_key_sequence()) {
if (g_resized) {
g_resized = false;
pager.resize();
}
if (!sequence_value.has_value()) {
continue;
}
auto const& sequence = sequence_value.value();
if (sequence.to_uint().has_value()) {
modifier_buffer.append(sequence);
} else {
if (sequence == "" || sequence == "q") {
break;
} else if (sequence == "j" || sequence == "\e[B" || sequence == "\n") {
if (!emulate_more) {
if (!modifier_buffer.is_empty())
pager.down_n(modifier_buffer.to_deprecated_string().to_uint().value_or(1));
else
pager.down();
}
} else if (sequence == "k" || sequence == "\e[A") {
if (!emulate_more) {
if (!modifier_buffer.is_empty())
pager.up_n(modifier_buffer.to_deprecated_string().to_uint().value_or(1));
else
pager.up();
}
} else if (sequence == "g") {
if (!emulate_more) {
if (!modifier_buffer.is_empty())
pager.go_to_line(modifier_buffer.to_deprecated_string().to_uint().value());
else
pager.top();
}
} else if (sequence == "G") {
if (!emulate_more) {
if (!modifier_buffer.is_empty())
pager.go_to_line(modifier_buffer.to_deprecated_string().to_uint().value());
else
pager.bottom();
}
} else if (sequence == " " || sequence == "f" || sequence == "\e[6~") {
pager.down_page();
} else if ((sequence == "\e[5~" || sequence == "b") && !emulate_more) {
pager.up_page();
} else if (sequence == "d") {
pager.down_half_page();
} else if (sequence == "u" && !emulate_more) {
pager.up_half_page();
}
modifier_buffer.clear();
}
if (quit_at_eof && pager.at_end())
break;
}
pager.clear_status();
TRY(teardown_tty(!dont_switch_buffer));
return 0;
}