Restructure to enable supporting stdin case

Ampretuzo · May 1, 2021 · 850428a · 850428a
1 parent eee45d2
commit 850428a
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Showing 2 changed files with 64 additions and 52 deletions.
diff --git a/initial-reverse/reverse.c b/initial-reverse/reverse.c
@@ -6,27 +6,81 @@
 #define fsame(stat1, stat2) (stat1.st_dev == stat2.st_dev && stat1.st_ino == stat2.st_ino)
 
 
-/* TODO: Error handling where applicable
+void reverse_seekable(FILE *in, FILE *out, FILE *err) {
+	char *line = NULL;
+	size_t line_len = 0;
+	fpos_t fpos_start;
+
+	fseek(in, 0, SEEK_END);
+
+	while (true) {
+		fgetpos(in, &fpos_start);
+		getline(&line, &line_len, in);
+		fprintf(out, "%s", line);
+		fsetpos(in, &fpos_start);
+
+		fseek(in, -1, SEEK_CUR);
+		if (ftell(in) <= 0) {
+			return;
+		}
+		bool last_char = true;
+		while (true) {
+			if (ftell(in) <= 0) {
+				break;
+			}
+			int c = fgetc(in);
+			if (!last_char && c == '\n') {
+				break;
+			}
+			last_char = false;
+			fseek(in, -2, SEEK_CUR);
+		}
+	}
+}
+
+void reverse(FILE *in, FILE *out, FILE *err) {
+	fprintf(err, "TODO");
+}
+
+
+/* TODO: Error handling where applicable (+ file closing and memory freeing)
  */
 int main(int argc, char *argv[]) {
-	if (argc < 2 || argc > 3) {
-		fprintf(stderr, "usage: reverse input [output]\n");
+	if (argc > 3) {
+		fprintf(stderr, "usage: reverse [input] [output]\n");
 		return 1;
 	}
 
+	if (argc == 1) {
+		reverse(stdin, stdout, stderr);
+		return 0;
+	}
+
 	char *input_filename;
-	char *output_filename;
 	FILE *input_file;
-	FILE *out;
 
 	input_filename = argv[1];
+	input_file = fopen(input_filename, "r");
+	if (!input_file) {
+		fprintf(stderr, "reverse: cannot open file '%s'\n", input_filename);
+		return 1;
+	}
+
+	if (argc == 2) {
+		reverse_seekable(input_file, stdout, stderr);
+		return 0;
+	}
 
-	if (argc > 2) {
+	if (argc == 3) {
+		char *output_filename;
+		FILE *out;
 		struct stat input_stat;
 		struct stat output_stat;
+
 		output_filename = argv[2];
+
 		if(stat(input_filename, &input_stat)) {
-			fprintf(stderr, "reverse: cannot open file '%s'\n", input_filename);
+			fprintf(stderr, "reverse: cannot stat file '%s'\n", input_filename);
 			return 1;
 		}
 		if(!stat(output_filename, &output_stat)) {
@@ -35,56 +89,14 @@ int main(int argc, char *argv[]) {
 				return 1;
 			}
 		}
-	}
-
-	input_file = fopen(input_filename, "r");
-	if (!input_file) {
-		fprintf(stderr, "reverse: cannot open file '%s'\n", input_filename);
-		return 1;
-	}
-
-	out = stdout;
-	if (output_filename) {
 		out = fopen(output_filename, "w");
 		if (!out) {
 			fprintf(stderr, "reverse: cannot open file '%s'\n", output_filename);
 			return 1;
 		}
+		reverse_seekable(input_file, out, stderr);
+		return 0;
 	}
 
-	char *line = NULL;
-	size_t line_len = 0;
-	fpos_t fpos_start;
-
-	// Actual program:
-
-	fseek(input_file, 0, SEEK_END);
-
-	while (true) {
-		fgetpos(input_file, &fpos_start);
-		getline(&line, &line_len, input_file);
-		fprintf(out, "%s", line);
-		fsetpos(input_file, &fpos_start);
-
-		// Position at the start of the previous line
-		fseek(input_file, -1, SEEK_CUR);
-		if (ftell(input_file) <= 0) {
-			return 0;
-		}
-		bool last_char = true;
-		while (true) {
-			if (ftell(input_file) <= 0) {
-				break;
-			}
-			int tmp = fgetc(input_file);
-			if (!last_char && tmp == '\n') {
-				break;
-			}
-			last_char = false;
-			fseek(input_file, -2, SEEK_CUR);
-		}
-	}
-
-	return 0;
 }
 
diff --git a/initial-reverse/tests/1.err b/initial-reverse/tests/1.err
@@ -1 +1 @@
-usage: reverse input [output]
+usage: reverse [input] [output]
Original file line number	Diff line number	Diff line change
		@@ -1 +1 @@
		usage: reverse input [output]
		usage: reverse [input] [output]