Add head and tail.

src/head.c

@@ -1,2 +1,270 @@
-#define PORTION 0
-#include "rev.c"
+#define _XOPEN_SOURCE	500
+
+#include <unistd.h>
+
+#include <errno.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define DEFAULT_LINE_CAPACITY	32
+#define DEFAULT_CHAR_CAPACITY	64
+
+#define MIN(x, y)		(((x) < (y)) ? (x) : (y))
+#define MAX(x, y)		(((x) > (y)) ? (x) : (y))
+
+static const char *argv0;
+
+static struct {
+	char **array;
+	size_t length;
+	size_t capacity;
+} lines;
+
+static struct {
+	char *array;
+	size_t length;
+	size_t capacity;
+} line;
+
+static enum {
+	MODE_BYTES,
+	MODE_LINES
+} mode;
+static size_t count;
+static bool quiet = false;
+
+static void append_to_line_list(void)
+{
+	char *str;
+
+	if (lines.length >= lines.capacity) {
+		void *ptr;
+		size_t new_capacity;
+
+		new_capacity = lines.capacity * 2;
+		ptr = realloc(lines.array, sizeof(char *) * new_capacity);
+		if (!ptr) {
+			fprintf(stderr, "%s: %s\n",
+				argv0, strerror(errno));
+			exit(-1);
+		}
+		lines.array = ptr;
+		lines.capacity = new_capacity;
+	}
+
+	str = malloc(line.length + 1);
+	if (!str) {
+		fprintf(stderr, "%s: %s\n",
+			argv0, strerror(errno));
+		exit(1);
+	}
+
+	memcpy(str, line.array, line.length);
+	str[line.length] = '\0';
+	lines.array[lines.length++] = str;
+}
+
+static void append_to_char_list(char ch)
+{
+	if (line.length >= line.capacity) {
+		void *ptr;
+		size_t new_capacity;
+
+		new_capacity = line.capacity * 2;
+		ptr = realloc(line.array, sizeof(char) * new_capacity);
+		if (!ptr) {
+			fprintf(stderr, "%s: %s\n",
+				argv0, strerror(errno));
+			exit(-1);
+		}
+		line.array = ptr;
+		line.capacity = new_capacity;
+	}
+	line.array[line.length++] = ch;
+}
+
+static void clear_lines(void)
+{
+	size_t i;
+
+	for (i = 0; i < lines.length; i++) {
+		free(lines.array[i]);
+	}
+	lines.length = 0;
+
+	free(line.array);
+	line.length = 0;
+}
+
+static void parse_arg(const char *arg)
+{
+	long num;
+	char *ptr;
+
+	num = strtol(optarg, &ptr, 0);
+	if (*ptr) {
+		fprintf(stderr, "%s: '%s' not a valid number for '%s'\n",
+			argv0, optarg, arg);
+		exit(1);
+	}
+	count = num;
+}
+
+static void print_file(const char *filename)
+{
+	size_t i;
+
+	if (filename && !quiet)
+		printf("[%s]\n", filename);
+
+#ifndef BOTTOM_SLICE
+	/* head */
+	switch (mode) {
+		case MODE_BYTES:
+			count = MIN(line.length, count);
+			if (fwrite(line.array, 1, count, stdout) < count) {
+				exit(1);
+			}
+			break;
+		case MODE_LINES:
+			count = MIN(lines.length, count);
+			for (i = 0; i < count; i++) {
+				puts(lines.array[i]);
+			}
+			break;
+		default:
+			abort();
+	}
+#else
+	/* tail */
+	switch (mode) {
+		case MODE_BYTES:
+			count = MIN(line.length, count);
+			if (fwrite(&line.array[line.length - count - 1], 1, count, stdout) < count) {
+				exit(1);
+			}
+			break;
+		case MODE_LINES:
+			count = MIN(lines.length, count);
+			for (i = lines.length - count - 1; i < lines.length; i++) {
+				puts(lines.array[i]);
+			}
+			break;
+		default:
+			abort();
+	}
+#endif /* !BOTTOM_SLICE */
+
+	if (filename && !quiet)
+		putchar('\n');
+}
+
+/* Usage: head [-n LINES] [-c bytes] [-q] [-v] [FILE...] */
+int main(int argc, char *argv[])
+{
+	int i, ch;
+
+	mode = MODE_LINES;
+	count = 10;
+
+	while ((ch = getopt(argc, argv, "n:c:qv")) != -1) {
+		switch (ch) {
+			case 'n':
+				parse_arg("-n");
+				break;
+			case 'c':
+				parse_arg("-c");
+				mode = MODE_BYTES;
+				break;
+			case 'q':
+				quiet = true;
+				break;
+			case 'v':
+				quiet = false;
+				break;
+			case '?':
+				return 1;
+			default:
+				abort();
+		}
+	}
+
+	lines.array = malloc(sizeof(char *) * DEFAULT_LINE_CAPACITY);
+	lines.length = 0;
+	lines.capacity = DEFAULT_LINE_CAPACITY;
+
+	if (!lines.array) {
+		fprintf(stderr, "%s: %s\n",
+				argv[0], strerror(errno));
+		return 1;
+	}
+
+	line.array = malloc(sizeof(char) * DEFAULT_CHAR_CAPACITY);
+	line.length = 0;
+	line.capacity = DEFAULT_CHAR_CAPACITY;
+
+	if (!line.array) {
+		fprintf(stderr, "%s: %s\n",
+				argv[0], strerror(errno));
+		return 1;
+	}
+
+	if (optind == argc) {
+		while ((ch = fgetc(stdin)) != EOF) {
+			if (ch == '\n' && mode == MODE_LINES) {
+				append_to_line_list();
+				line.length = 0;
+#ifndef BOTTOM_SLICE
+				/* head */
+				if (lines.length >= count)
+					break;
+#endif /* !BOTTOM_SLICE */
+			} else {
+				append_to_char_list(ch);
+#ifndef BOTTOM_SLICE
+				/* head */
+				if (mode == MODE_BYTES && line.length >= count)
+					break;
+#endif /* !BOTTOM_SLICE */
+			}
+		}
+		if (mode == MODE_LINES) {
+			append_to_line_list();
+		}
+		print_file(NULL);
+	} else {
+		for (i = optind; i < argc; i++) {
+			FILE *fh;
+
+			if (!strcmp(argv[i], "-"))
+				fh = stdin;
+			else
+				fh = fopen(argv[i], "r");
+
+			if (!fh)
+				return 1;
+			while ((ch = fgetc(fh)) != EOF) {
+				if (ch == '\n' && mode == MODE_LINES) {
+					append_to_line_list();
+					line.length = 0;
+				} else {
+					append_to_char_list(ch);
+				}
+			}
+			if (fclose(fh)) {
+				fprintf(stderr, "%s: %s\n",
+						argv[0], strerror(errno));
+				return 1;
+			}
+			if (mode == MODE_LINES) {
+				append_to_line_list();
+			}
+			print_file(argv[i]);
+			clear_lines();
+		}
+	}
+
+	return 0;
+}

src/rev.c

@@ -58,7 +58,7 @@ static void append_to_char_list(char ch)
 		void *ptr;
 		size_t new_capacity;
 
-		new_capacity = lines.capacity * 2;
+		new_capacity = line.capacity * 2;
 		ptr = realloc(line.array, sizeof(char) * new_capacity);
 		if (!ptr) {
 			fprintf(stderr, "%s: %s\n",
@@ -80,15 +80,22 @@ int main(int argc, char *argv[])
 	lines.length = 0;
 	lines.capacity = DEFAULT_LINE_CAPACITY;
 
+	if (!lines.array) {
+		fprintf(stderr, "%s: %s\n",
+			argv[0], strerror(errno));
+		return 1;
+	}
+
 	line.array = malloc(sizeof(char) * DEFAULT_CHAR_CAPACITY);
 	line.length = 0;
 	line.capacity = DEFAULT_CHAR_CAPACITY;
 
-	if (!lines.array) {
+	if (!line.array) {
 		fprintf(stderr, "%s: %s\n",
 			argv[0], strerror(errno));
 		return 1;
 	}
+
 	if (argc == 1) {
 		int ch;
 
@@ -131,17 +138,7 @@ int main(int argc, char *argv[])
 	}
 
 	free(line.array);
-#if defined(PORTION)
-	/* head */
-	for (i = 0; i < PORTION_LINES; i++) {
-# if PORTION == 0 /* head */
-		const size_t index = i;
-# else
-		const size_t index = lines.length - PORTION_LINES + i - 1;
-# endif /* PORTION */
-		puts(lines.array[index]);
-	}
-#elif defined(REVERSE_LINES)
+#if defined(REVERSE_LINES)
 	/* tac */
 	for (i = lines.length - 1; i >= 0; i--)
 		puts(lines.array[i]);

src/tail.c

@@ -1,2 +1,2 @@
-#define PORTION 1
-#include "rev.c"
+#define BOTTOM_SLICE
+#include "head.c"