Aegisub/src/subtitle_format_srt.cpp

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// Copyright (c) 2006, Rodrigo Braz Monteiro
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
// * Neither the name of the Aegisub Group nor the names of its contributors
// may be used to endorse or promote products derived from this software
// without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
//
// Aegisub Project http://www.aegisub.org/
/// @file subtitle_format_srt.cpp
/// @brief Reading/writing SubRip format subtitles (.SRT)
/// @ingroup subtitle_io
///
#include "subtitle_format_srt.h"
#include "ass_attachment.h"
#include "ass_dialogue.h"
#include "ass_file.h"
#include "options.h"
#include "text_file_reader.h"
#include "text_file_writer.h"
#include <libaegisub/format.h>
#include <libaegisub/of_type_adaptor.h>
#include <boost/algorithm/string/case_conv.hpp>
#include <boost/algorithm/string/predicate.hpp>
#include <boost/algorithm/string/replace.hpp>
#include <boost/algorithm/string/trim.hpp>
#include <boost/regex.hpp>
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DEFINE_EXCEPTION(SRTParseError, SubtitleFormatParseError);
namespace {
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enum class TagType {
UNKNOWN,
BOLD_OPEN,
BOLD_CLOSE,
ITALICS_OPEN,
ITALICS_CLOSE,
UNDERLINE_OPEN,
UNDERLINE_CLOSE,
STRIKEOUT_OPEN,
STRIKEOUT_CLOSE,
FONT_OPEN,
FONT_CLOSE
};
TagType type_from_name(std::string const& tag) {
switch (tag.size()) {
case 1:
switch (tag[0]) {
case 'b': return TagType::BOLD_OPEN;
case 'i': return TagType::ITALICS_OPEN;
case 'u': return TagType::UNDERLINE_OPEN;
case 's': return TagType::STRIKEOUT_OPEN;
default: return TagType::UNKNOWN;
}
case 2:
if (tag[0] != '/') return TagType::UNKNOWN;
switch (tag[1]) {
case 'b': return TagType::BOLD_CLOSE;
case 'i': return TagType::ITALICS_CLOSE;
case 'u': return TagType::UNDERLINE_CLOSE;
case 's': return TagType::STRIKEOUT_CLOSE;
default: return TagType::UNKNOWN;
}
default:
if (tag == "font") return TagType::FONT_OPEN;
if (tag == "/font") return TagType::FONT_CLOSE;
return TagType::UNKNOWN;
}
}
struct ToggleTag {
char tag;
int level = 0;
ToggleTag(char tag) : tag(tag) { }
void Open(std::string& out) {
if (level == 0) {
out += "{\\";
out += tag;
out += "1}";
}
++level;
}
void Close(std::string& out) {
if (level == 1) {
out += "{\\";
out += tag;
out += '}';
}
if (level > 0)
--level;
}
};
class SrtTagParser {
struct FontAttribs {
std::string face;
std::string size;
std::string color;
};
const boost::regex tag_matcher;
const boost::regex attrib_matcher;
const boost::regex is_quoted;
public:
SrtTagParser()
: tag_matcher("^(.*?)<(/?b|/?i|/?u|/?s|/?font)([^>]*)>(.*)$", boost::regex::icase)
, attrib_matcher(R"(^[[:space:]]+(face|size|color)=('[^']*'|"[^"]*"|[^[:space:]]+))", boost::regex::icase)
, is_quoted(R"(^(['"]).*\1$)")
{
}
std::string ToAss(std::string srt)
{
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ToggleTag bold('b');
ToggleTag italic('i');
ToggleTag underline('u');
ToggleTag strikeout('s');
std::vector<FontAttribs> font_stack;
std::string ass; // result to be built
while (!srt.empty())
{
boost::smatch result;
if (!regex_match(srt, result, tag_matcher))
{
// no more tags could be matched, end of string
ass.append(srt);
break;
}
// we found a tag, translate it
std::string pre_text = result.str(1);
std::string tag_name = result.str(2);
std::string tag_attrs = result.str(3);
std::string post_text = result.str(4);
// the text before the tag goes through unchanged
ass.append(pre_text);
// the text after the tag is the input for next iteration
srt = post_text;
boost::to_lower(tag_name);
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switch (type_from_name(tag_name))
{
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case TagType::BOLD_OPEN: bold.Open(ass); break;
case TagType::BOLD_CLOSE: bold.Close(ass); break;
case TagType::ITALICS_OPEN: italic.Open(ass); break;
case TagType::ITALICS_CLOSE: italic.Close(ass); break;
case TagType::UNDERLINE_OPEN: underline.Open(ass); break;
case TagType::UNDERLINE_CLOSE: underline.Close(ass); break;
case TagType::STRIKEOUT_OPEN: strikeout.Open(ass); break;
case TagType::STRIKEOUT_CLOSE: strikeout.Close(ass); break;
case TagType::FONT_OPEN:
{
// new attributes to fill in
FontAttribs new_attribs;
FontAttribs old_attribs;
// start out with any previous ones on stack
if (font_stack.size() > 0)
old_attribs = font_stack.back();
new_attribs = old_attribs;
// now find all attributes on this font tag
boost::smatch result;
while (regex_search(tag_attrs, result, attrib_matcher))
{
// get attribute name and values
std::string attr_name = result.str(1);
std::string attr_value = result.str(2);
// clean them
boost::to_lower(attr_name);
if (regex_match(attr_value, is_quoted))
attr_value = attr_value.substr(1, attr_value.size() - 2);
// handle the attributes
if (attr_name == "face")
new_attribs.face = agi::format("{\\fn%s}", attr_value);
else if (attr_name == "size")
new_attribs.size = agi::format("{\\fs%s}", attr_value);
else if (attr_name == "color")
new_attribs.color = agi::format("{\\c%s}", agi::Color(attr_value).GetAssOverrideFormatted());
// remove this attribute to prepare for the next
tag_attrs = result.suffix().str();
}
// the attributes changed from old are then written out
if (new_attribs.face != old_attribs.face)
ass.append(new_attribs.face);
if (new_attribs.size != old_attribs.size)
ass.append(new_attribs.size);
if (new_attribs.color != old_attribs.color)
ass.append(new_attribs.color);
// lastly dump the new attributes state onto the stack
font_stack.push_back(new_attribs);
}
break;
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case TagType::FONT_CLOSE:
{
// this requires a font stack entry
if (font_stack.empty())
break;
// get the current attribs
FontAttribs cur_attribs = font_stack.back();
// remove them from the stack
font_stack.pop_back();
// grab the old attributes if there are any
FontAttribs old_attribs;
if (font_stack.size() > 0)
old_attribs = font_stack.back();
// then restore the attributes to previous settings
if (cur_attribs.face != old_attribs.face)
{
if (old_attribs.face.empty())
ass.append("{\\fn}");
else
ass.append(old_attribs.face);
}
if (cur_attribs.size != old_attribs.size)
{
if (old_attribs.size.empty())
ass.append("{\\fs}");
else
ass.append(old_attribs.size);
}
if (cur_attribs.color != old_attribs.color)
{
if (old_attribs.color.empty())
ass.append("{\\c}");
else
ass.append(old_attribs.color);
}
}
break;
default:
// unknown tag, replicate it in the output
ass.append("<").append(tag_name).append(tag_attrs).append(">");
break;
}
}
// make it a little prettier, join tag groups
boost::replace_all(ass, "}{", "");
return ass;
}
};
std::string WriteSRTTime(agi::Time const& ts)
{
return ts.GetSrtFormatted();
}
}
SRTSubtitleFormat::SRTSubtitleFormat()
: SubtitleFormat("SubRip")
{
}
std::vector<std::string> SRTSubtitleFormat::GetReadWildcards() const {
return {"srt"};
}
std::vector<std::string> SRTSubtitleFormat::GetWriteWildcards() const {
return GetReadWildcards();
}
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enum class ParseState {
INITIAL,
TIMESTAMP,
FIRST_LINE_OF_BODY,
REST_OF_BODY,
LAST_WAS_BLANK
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};
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void SRTSubtitleFormat::ReadFile(AssFile *target, agi::fs::path const& filename, agi::vfr::Framerate const& fps, std::string const& encoding) const {
using namespace std;
TextFileReader file(filename, encoding);
target->LoadDefault(false, OPT_GET("Subtitle Format/SRT/Default Style Catalog")->GetString());
// See parsing algorithm at <http://devel.aegisub.org/wiki/SubtitleFormats/SRT>
// "hh:mm:ss,fff --> hh:mm:ss,fff" (e.g. "00:00:04,070 --> 00:00:10,04")
const boost::regex timestamp_regex("^([0-9]{1,2}:[0-9]{1,2}:[0-9]{1,2},[0-9]{1,}) --> ([0-9]{1,2}:[0-9]{1,2}:[0-9]{1,2},[0-9]{1,})");
SrtTagParser tag_parser;
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ParseState state = ParseState::INITIAL;
int line_num = 0;
int linebreak_debt = 0;
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AssDialogue *line = nullptr;
std::string text;
while (file.HasMoreLines()) {
std::string text_line = file.ReadLineFromFile();
++line_num;
boost::trim(text_line);
boost::smatch timestamp_match;
bool found_timestamps = false;
switch (state) {
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case ParseState::INITIAL:
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// ignore leading blank lines
if (text_line.empty()) break;
if (all(text_line, boost::is_digit())) {
// found the line number, throw it away and hope for timestamps
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state = ParseState::TIMESTAMP;
break;
}
if (regex_search(text_line, timestamp_match, timestamp_regex)) {
found_timestamps = true;
break;
}
throw SRTParseError(agi::format("Parsing SRT: Expected subtitle index at line %d", line_num));
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case ParseState::TIMESTAMP:
if (!regex_search(text_line, timestamp_match, timestamp_regex))
throw SRTParseError(agi::format("Parsing SRT: Expected timestamp pair at line %d", line_num));
found_timestamps = true;
break;
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case ParseState::FIRST_LINE_OF_BODY:
if (text_line.empty()) {
// that's not very interesting... blank subtitle?
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state = ParseState::LAST_WAS_BLANK;
// no previous line that needs a line break after
linebreak_debt = 0;
break;
}
text.append(text_line);
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state = ParseState::REST_OF_BODY;
break;
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case ParseState::REST_OF_BODY:
if (text_line.empty()) {
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// Might be either the gap between two subtitles or just a
// blank line in the middle of a subtitle, so defer adding
// the line break until we check what's on the next line
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state = ParseState::LAST_WAS_BLANK;
linebreak_debt = 1;
break;
}
text.append("\\N");
text.append(text_line);
break;
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case ParseState::LAST_WAS_BLANK:
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++linebreak_debt;
if (text_line.empty()) break;
if (all(text_line, boost::is_digit())) {
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// Hopefully it's the start of a new subtitle, and the
// previous blank line(s) were the gap between subtitles
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state = ParseState::TIMESTAMP;
break;
}
if (regex_search(text_line, timestamp_match, timestamp_regex)) {
found_timestamps = true;
break;
}
// assume it's a continuation of the subtitle text
// resolve our line break debt and append the line text
while (linebreak_debt-- > 0)
text.append("\\N");
text.append(text_line);
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state = ParseState::REST_OF_BODY;
break;
}
if (found_timestamps) {
if (line) {
// finalize active line
line->Text = tag_parser.ToAss(text);
text.clear();
}
// create new subtitle
line = new AssDialogue;
line->Start = timestamp_match.str(1);
line->End = timestamp_match.str(2);
// store pointer to subtitle, we'll continue working on it
target->Events.push_back(*line);
// next we're reading the text
state = ParseState::FIRST_LINE_OF_BODY;
}
}
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if (state == ParseState::TIMESTAMP || state == ParseState::FIRST_LINE_OF_BODY)
throw SRTParseError("Parsing SRT: Incomplete file");
if (line) // an unfinalized line
line->Text = tag_parser.ToAss(text);
}
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void SRTSubtitleFormat::WriteFile(const AssFile *src, agi::fs::path const& filename, agi::vfr::Framerate const& fps, std::string const& encoding) const {
TextFileWriter file(filename, encoding);
// Convert to SRT
AssFile copy(*src);
copy.Sort();
StripComments(copy);
RecombineOverlaps(copy);
MergeIdentical(copy);
#ifdef _WIN32
ConvertNewlines(copy, "\r\n", false);
#else
ConvertNewlines(copy, "\n", false);
#endif
// Write lines
int i=0;
for (auto const& current : copy.Events) {
file.WriteLineToFile(std::to_string(++i));
file.WriteLineToFile(WriteSRTTime(current.Start) + " --> " + WriteSRTTime(current.End));
file.WriteLineToFile(ConvertTags(&current));
file.WriteLineToFile("");
}
}
bool SRTSubtitleFormat::CanSave(const AssFile *file) const {
if (!file->Attachments.empty())
return false;
auto def = boost::flyweight<std::string>("Default");
for (auto const& line : file->Events) {
if (line.Style != def)
return false;
auto blocks = line.ParseTags();
for (auto ovr : blocks | agi::of_type<AssDialogueBlockOverride>()) {
// Verify that all overrides used are supported
for (auto const& tag : ovr->Tags) {
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if (tag.Name.size() != 2)
return false;
if (!strchr("bisu", tag.Name[1]))
return false;
}
}
}
return true;
}
std::string SRTSubtitleFormat::ConvertTags(const AssDialogue *diag) const {
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struct tag_state { char tag; bool value; };
tag_state tag_states[] = {
{'b', false},
{'i', false},
{'s', false},
{'u', false}
};
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std::string final;
for (auto& block : diag->ParseTags()) {
switch (block->GetType()) {
case AssBlockType::OVERRIDE:
for (auto const& tag : static_cast<AssDialogueBlockOverride&>(*block).Tags) {
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if (!tag.IsValid() || tag.Name.size() != 2)
continue;
for (auto& state : tag_states) {
if (state.tag != tag.Name[1]) continue;
bool temp = tag.Params[0].Get(false);
if (temp && !state.value)
final += agi::format("<%c>", state.tag);
if (!temp && state.value)
final += agi::format("</%c>", state.tag);
state.value = temp;
}
}
break;
case AssBlockType::PLAIN:
final += block->GetText();
break;
case AssBlockType::DRAWING:
case AssBlockType::COMMENT:
break;
}
}
// Ensure all tags are closed
// Otherwise unclosed overrides might affect lines they shouldn't, see bug #809 for example
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for (auto state : tag_states) {
if (state.value)
final += agi::format("</%c>", state.tag);
}
return final;
}