Add hi syntax highlighter

2 files changed, 345 insertions, 0 deletions

diff --git a/bin/hi.c b/bin/hi.c
new file mode 100644
index 00000000..965de239
--- /dev/null
+++ b/bin/hi.c
@@ -0,0 +1,283 @@
+/* Copyright (C) 2019  C. McEnroe <june@causal.agency>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <err.h>
+#include <regex.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sysexits.h>
+#include <unistd.h>
+
+#define ARRAY_LEN(a) (sizeof(a) / sizeof(a[0]))
+
+enum Class {
+	Normal,
+	Keyword,
+	Macro,
+	Comment,
+	String,
+	ClassCount,
+};
+
+struct Syntax {
+	enum Class class;
+	int flags;
+	const char *pattern;
+};
+
+// FIXME: Looks like [[:<:]] [[:>:]] are not supported on GNU.
+static const struct Syntax CSyntax[] = {
+	{ Keyword, 0,            "[[:<:]](enum|struct|typedef|union)[[:>:]]" },
+	{ Keyword, 0,            "[[:<:]](const|inline|static)[[:>:]]" },
+	{ Keyword, 0,            "[[:<:]](do|else|for|if|switch|while)[[:>:]]" },
+	{ Keyword, 0,            "[[:<:]](break|continue|goto|return)[[:>:]]" },
+	{ Keyword, 0,            "[[:<:]](case|default)[[:>:]]" },
+	{ Macro,   REG_NEWLINE,  "^#.*" },
+	{ String,  REG_NEWLINE,  "<[^[:blank:]=]*>" },
+	{ Comment, REG_NEWLINE,  "//.*" },
+	{ Comment, REG_ENHANCED, "/\\*.*?\\*/" }, // FIXME: Darwin-only.
+	{ String,  REG_NEWLINE,  "[LUu]?'([^']|\\\\')*'" },
+	{ String,  REG_NEWLINE,  "([LUu]|u8)?\"([^\"]|\\\\\")*\"" },
+};
+
+static const struct Language {
+	const char *name;
+	const char *pattern;
+	const struct Syntax *syntax;
+	size_t len;
+} Languages[] = {
+	{ "c", "\\.[ch]$", CSyntax, ARRAY_LEN(CSyntax) },
+};
+
+static regex_t compile(const char *pattern, int flags) {
+	regex_t regex;
+	int error = regcomp(&regex, pattern, REG_EXTENDED | flags);
+	if (!error) return regex;
+	char buf[256];
+	regerror(error, &regex, buf, sizeof(buf));
+	errx(EX_SOFTWARE, "regcomp: %s: %s", buf, pattern);
+}
+
+static void highlight(struct Language lang, enum Class *hi, const char *str) {
+	for (size_t i = 0; i < lang.len; ++i) {
+		regex_t regex = compile(lang.syntax[i].pattern, lang.syntax[i].flags);
+		regmatch_t match = {0};
+		for (size_t offset = 0; str[offset]; offset += match.rm_eo) {
+			int error = regexec(
+				&regex, &str[offset], 1, &match, offset ? REG_NOTBOL : 0
+			);
+			if (error == REG_NOMATCH) break;
+			if (error) errx(EX_SOFTWARE, "regexec: %d", error);
+			for (regoff_t j = match.rm_so; j < match.rm_eo; ++j) {
+				hi[offset + j] = lang.syntax[i].class;
+			}
+		}
+		regfree(&regex);
+	}
+}
+
+typedef void HeaderFn(const char *path);
+typedef void OutputFn(enum Class class, const char *str, size_t len);
+
+enum SGR {
+	Reset, Bold,
+	Black = 30, Red, Green, Yellow, Blue, Magenta, Cyan, White, Default,
+};
+
+static const enum SGR Style[ClassCount][2] = {
+	[Normal]  = { Reset, Default },
+	[Keyword] = { Reset, White },
+	[Macro]   = { Reset, Green },
+	[Comment] = { Reset, Blue },
+	[String]  = { Reset, Cyan },
+};
+
+static void ansiOutput(enum Class class, const char *str, size_t len) {
+	// Style each line separately, otherwise less -R won't look right.
+	while (len) {
+		size_t line = strcspn(str, "\n") + 1;
+		if (line > len) line = len;
+		printf(
+			"\x1B[%d;%dm%.*s\x1B[%dm",
+			Style[class][0], Style[class][1], (int)line, str, Style[class][0]
+		);
+		str += line;
+		len -= line;
+	}
+}
+
+static void htmlHeader(const char *path) {
+	(void)path;
+	printf("<pre>");
+}
+static void htmlFooter(const char *path) {
+	(void)path;
+	printf("</pre>\n");
+}
+
+static void htmlEscape(const char *str, size_t len) {
+	while (len) {
+		size_t run = strcspn(str, "&<>");
+		if (run > len) run = len;
+		switch (str[0]) {
+			break; case '&': run = 1; printf("&amp;");
+			break; case '<': run = 1; printf("&lt;");
+			break; case '>': run = 1; printf("&gt;");
+			break; default:  printf("%.*s", (int)run, str);
+		}
+		str += run;
+		len -= run;
+	}
+}
+
+static const char *ClassName[ClassCount] = {
+	[Normal]  = "Normal",
+	[Keyword] = "Keyword",
+	[Macro]   = "Macro",
+	[Comment] = "Comment",
+	[String]  = "String",
+};
+
+static void htmlOutput(enum Class class, const char *str, size_t len) {
+	printf("<span class=\"hi %s\">", ClassName[class]);
+	htmlEscape(str, len);
+	printf("</span>");
+}
+
+static void htmlDocumentHeader(const char *path) {
+	const char *slash = strrchr(path, '/');
+	if (slash) path = &slash[1];
+	printf("<!DOCTYPE html>\n<title>");
+	htmlEscape(path, strlen(path));
+	printf(
+		"</title>\n"
+		"<style>\n"
+		".hi.Keyword { color: dimgray; }\n"
+		".hi.Macro   { color: green; }\n"
+		".hi.Comment { color: navy; }\n"
+		".hi.String  { color: teal; }\n"
+		"</style>\n"
+	);
+	htmlHeader(path);
+}
+
+static const struct Format {
+	const char *name;
+	OutputFn *output;
+	HeaderFn *header;
+	HeaderFn *footer;
+} Formats[] = {
+	{ "ansi", ansiOutput, NULL, NULL },
+	{ "html", htmlOutput, htmlHeader, htmlFooter },
+	{ "html-document", htmlOutput, htmlDocumentHeader, htmlFooter },
+};
+
+int main(int argc, char *argv[]) {
+	bool check = false;
+	const struct Language *lang = NULL;
+	const struct Format *format = NULL;
+	
+	int opt;
+	while (0 < (opt = getopt(argc, argv, "cf:l:"))) {
+		switch (opt) {
+			break; case 'c': check = true;
+			break; case 'f': {
+				for (size_t i = 0; i < ARRAY_LEN(Formats); ++i) {
+					if (strcmp(optarg, Formats[i].name)) continue;
+					format = &Formats[i];
+					break;
+				}
+				if (!format) errx(EX_USAGE, "no such format %s", optarg);
+			}
+			break; case 'l': {
+				for (size_t i = 0; i < ARRAY_LEN(Languages); ++i) {
+					if (strcmp(optarg, Languages[i].name)) continue;
+					lang = &Languages[i];
+					break;
+				}
+				if (!lang) errx(EX_USAGE, "no such language %s", optarg);
+			}
+			break; default: return EX_USAGE;
+		}
+	}
+
+	if (check) {
+		for (size_t i = 0; i < ARRAY_LEN(Languages); ++i) {
+			regex_t regex = compile(Languages[i].pattern, REG_NOSUB);
+			regfree(&regex);
+			for (size_t j = 0; j < Languages[i].len; ++j) {
+				regex = compile(Languages[i].syntax[j].pattern, REG_NOSUB);
+				regfree(&regex);
+			}
+		}
+		return EX_OK;
+	}
+
+	const char *path = "(stdin)";
+	FILE *file = stdin;
+	if (optind < argc) {
+		path = argv[optind];
+		file = fopen(path, "r");
+		if (!file) err(EX_NOINPUT, "%s", path);
+	}
+
+	if (!lang) {
+		for (size_t i = 0; i < ARRAY_LEN(Languages); ++i) {
+			regex_t regex = compile(Languages[i].pattern, REG_NOSUB);
+			bool match = !regexec(&regex, path, 0, NULL, 0);
+			regfree(&regex);
+			if (match) {
+				lang = &Languages[i];
+				break;
+			}
+		}
+		if (!lang) errx(EX_USAGE, "cannot infer language for %s", path);
+	}
+	if (!format) format = &Formats[0];
+
+	size_t len = 32 * 1024;
+	if (file != stdin) {
+		struct stat stat;
+		int error = fstat(fileno(file), &stat);
+		if (error) err(EX_IOERR, "fstat");
+		len = stat.st_size;
+	}
+
+	char *str = malloc(len + 1);
+	if (!str) err(EX_OSERR, "malloc");
+
+	len = fread(str, 1, len, file);
+	if (ferror(file)) err(EX_IOERR, "fread");
+	str[len] = '\0';
+
+	enum Class *hi = calloc(len, sizeof(*hi));
+	if (!hi) err(EX_OSERR, "calloc");
+
+	highlight(*lang, hi, str);
+
+	if (format->header) format->header(path);
+	size_t run = 0;
+	for (size_t i = 0; i < len; i += run) {
+		for (run = 0; i + run < len; ++run) {
+			if (hi[i + run] != hi[i]) break;
+		}
+		format->output(hi[i], &str[i], run);
+	}
+	if (format->footer) format->footer(path);
+}
diff --git a/bin/man1/hi.1 b/bin/man1/hi.1
new file mode 100644
index 00000000..5ed72061
--- /dev/null
+++ b/bin/man1/hi.1
@@ -0,0 +1,62 @@
+.Dd February 6, 2019
+.Dt HI 1
+.Os
+.
+.Sh NAME
+.Nm hi
+.Nd syntax highlighter
+.
+.Sh SYNOPSIS
+.Nm
+.Op Fl f Ar format
+.Op Fl l Ar lang
+.Op Ar file
+.Nm
+.Fl c
+.
+.Sh DESCRIPTION
+.Nm
+highlights the contents of a
+.Ar file
+or standard input
+and formats it
+on standard output.
+.
+.Pp
+The arguments are as follows:
+.Bl -tag -width Ds
+.It Fl c
+Compile all regular expressions and exit.
+.It Fl f Ar format
+Set the output format.
+The default
+.Ar format
+is
+.Cm ansi .
+.It Fl l Ar lang
+Set the input language.
+If a
+.Ar file
+is provided,
+.Ar lang
+may be inferred from its name.
+.El
+.
+.Pp
+The following languages are supported:
+.Cm c .
+.
+.Pp
+The output formats are as follows:
+.Bl -tag -width "html-document"
+.It Cm ansi
+ANSI terminal escape codes.
+.It Cm html
+HTML
+.Sy <pre>
+fragment with
+.Sy <span>
+classes.
+.It Cm html-document
+HTML document with default styles.
+.El