From ad20c5466321f6c8bd3006953b3b37e50935cdb4 Mon Sep 17 00:00:00 2001
From: "B. Watson" <urchlay@slackware.uk>
Date: Sat, 29 Jun 2024 21:45:25 -0400
Subject: a8xd: implement -o, -s, -l, add more messages for -v.

---
 a8xd.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 59 insertions(+), 14 deletions(-)

(limited to 'a8xd.c')

diff --git a/a8xd.c b/a8xd.c
index c322624..f051c4b 100644
--- a/a8xd.c
+++ b/a8xd.c
@@ -54,7 +54,6 @@ void parse_seek_arg(const char *arg) {
 
 	if(*arg == '-') {
 		seek_whence = SEEK_END;
-		arg++;
 	}
 
 	seekpos = parse_num_arg(arg);
@@ -64,8 +63,6 @@ int parse_offset_arg(const char *arg) {
 	int got;
 
 	got = parse_num_arg(arg);
-	if(got < 0)
-		die("negative arguments to -o (offset) are not supported.");
 
 	return got;
 }
@@ -84,22 +81,24 @@ FILE *open_input(const char *file) {
 	FILE *input;
 
 	if(file[0] == '-' && file[1] == 0) {
-		if(verbose)
-			fprintf(stderr, "%s: reading from standard input.\n", self);
 		if(freopen(NULL, "rb", stdin)) {
 			input = stdin;
 		} else {
+			fprintf(stderr, "%s: ", self);
 			perror("(standard input)");
 			return NULL;
 		}
-	} else if(!(input = fopen(file, "rb"))) {
-		perror(file);
-		return NULL;
+		if(verbose)
+			fprintf(stderr, "%s: reading from standard input.\n", self);
+	} else {
+		if(!(input = fopen(file, "rb"))) {
+			perror(file);
+			return NULL;
+		}
+		if(verbose)
+			fprintf(stderr, "%s: reading from file '%s'.\n", self, file);
 	}
 
-	if(verbose)
-		fprintf(stderr, "%s: reading from file '%s'.\n", self, file);
-
 	return input;
 }
 
@@ -128,6 +127,44 @@ char *get_color(unsigned char c) {
 	return outbuf;
 }
 
+void fake_seek(FILE *input) {
+	char junkbuf[1024];
+	int pos = 0, chunksize;
+
+	if(verbose)
+		fprintf(stderr, "%s: faking fseek() for stdin, skipping %d bytes.\n", self, seekpos);
+
+	while(pos < seekpos) {
+		chunksize = seekpos - pos;
+		if(chunksize > 1024) chunksize = 1024;
+		if(fread(junkbuf, 1, chunksize, input) != chunksize)
+			die("can't seek past end of input");
+		pos += chunksize;
+	}
+}
+
+void seek_input(FILE *input) {
+	if(verbose)
+		fprintf(stderr, "%s: seeking %d bytes (whence = %d) in input.\n", self, seekpos, seek_whence);
+	if(input == stdin) {
+		/* can't fseek() a stream, fake it */
+		if(seek_whence != SEEK_SET)
+			die("can't seek from the end of standard input.");
+		fake_seek(input);
+	} else {
+		if(fseek(input, seekpos, seek_whence) < 0) {
+			fprintf(stderr, "%s: ", self);
+			perror("fseek() failed");
+			exit(1);
+		}
+		if((filepos = ftell(input)) < 0) {
+			fprintf(stderr, "%s: ", self);
+			perror("ftell() failed");
+			exit(1);
+		}
+	}
+}
+
 void dump_line(const unsigned char *buf, int len) {
 	char hex[1024], asc[1024];
 	int hpos = 0, apos = 0, count = len;
@@ -165,13 +202,17 @@ void dump_line(const unsigned char *buf, int len) {
 
 int a8xd(const char *file) {
 	FILE *input;
-	int c, len = 0;
+	int c, len = 0, count = 0;
 	unsigned char buf[16];
 
 	if( !(input = open_input(file)) )
 		return 1;
 
+	if(seekpos) seek_input(input);
+
 	while( (c = fgetc(input)) != EOF ) {
+		if(limit && (count == limit)) break;
+		count++;
 		if(len && (len % 16 == 0)) {
 			dump_line(buf, len);
 			len = 0;
@@ -181,6 +222,10 @@ int a8xd(const char *file) {
 
 	if(len) dump_line(buf, len);
 
+	if(verbose)
+		fprintf(stderr, "%s: dumped %d (0x%04x) bytes from '%s'.\n", self, count, count, file);
+
+	fclose(input);
 	return 0;
 }
 
@@ -199,7 +244,7 @@ int main(int argc, char **argv) {
 		exit(0);
 	}
 
-	while( (opt = getopt(argc, argv, "vimus:o:l")) != -1) {
+	while( (opt = getopt(argc, argv, "vimus:o:l:")) != -1) {
 		switch(opt) {
 			case 'v': verbose = 1; break;
 			case 'i': table = ics2utf; break;
@@ -207,7 +252,7 @@ int main(int argc, char **argv) {
 			case 'u': word_format = "%04X"; byte_format = "%02X"; break;
 			case 's': parse_seek_arg(optarg); break;
 			case 'o': disp_offset = parse_offset_arg(optarg); break;
-			case 'l': disp_offset = parse_limit_arg(optarg); break;
+			case 'l': limit = parse_limit_arg(optarg); break;
 			default: print_help(); exit(1); break;
 		}
 	}
-- 
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