inotail.c: Reorder lines_to_offset* functions

Make lines_to_offset() just a wrapper function to check whether to tail
from begin or from end of the file. The real work is done in
lines_to_offset_from_begin() and lines_to_offset_from_end()

1 files changed, 37 insertions, 31 deletions

diff --git a/inotail.c b/inotail.c
index 8a9e1a9..7b58477 100644
--- a/inotail.c
+++ b/inotail.c
@@ -99,21 +99,23 @@ static void write_header(char *filename)
 	first_file = 0;
 }
 
-static off_t lines_to_offset_from_begin(struct file_struct *f, unsigned int n_lines)
+static off_t lines_to_offset_from_end(struct file_struct *f, unsigned int n_lines)
 {
 	char buf[BUFFER_SIZE];
-	off_t offset = 0;
-
-	/* tail everything for 'inotail -n +0' */
-	if (n_lines == 0)
-		return 0;
+	off_t offset = f->st_size;
 
-	n_lines--;
+	n_lines++;	/* We also count the last \n */
 	memset(&buf, 0, sizeof(buf));
 
-	while (offset <= f->st_size && n_lines > 0) {
+	while (offset > 0 && n_lines > 0) {
 		int i, rc;
-		int block_size = BUFFER_SIZE;
+		int block_size = BUFFER_SIZE;	/* Size of the current block we're reading */
+
+		if (offset < BUFFER_SIZE)
+			block_size = offset;
+
+		/* Start of current block */
+		offset -= block_size;
 
 		lseek(f->fd, offset, SEEK_SET);
 
@@ -123,42 +125,37 @@ static off_t lines_to_offset_from_begin(struct file_struct *f, unsigned int n_li
 			return -1;
 		}
 
-		for (i = 0; i < block_size; i++) {
+		for (i = block_size; i > 0; i--) {
 			if (buf[i] == '\n') {
 				n_lines--;
+
 				if (n_lines == 0) {
-					offset += i + 1;
-					return offset;
+					offset += i + 1; /* We don't want the first \n */
+					break;
 				}
 			}
 		}
-
-		offset += block_size;
 	}
 
 	return offset;
+
 }
 
-static off_t lines_to_offset(struct file_struct *f, unsigned int n_lines)
+static off_t lines_to_offset_from_begin(struct file_struct *f, unsigned int n_lines)
 {
 	char buf[BUFFER_SIZE];
-	off_t offset = f->st_size;
+	off_t offset = 0;
 
-	if (from_begin)
-		return lines_to_offset_from_begin(f, n_lines);
+	/* tail everything for 'inotail -n +0' */
+	if (n_lines == 0)
+		return 0;
 
-	n_lines++;	/* We also count the last \n */
+	n_lines--;
 	memset(&buf, 0, sizeof(buf));
 
-	while (offset > 0 && n_lines > 0) {
+	while (offset <= f->st_size && n_lines > 0) {
 		int i, rc;
-		int block_size = BUFFER_SIZE;	/* Size of the current block we're reading */
-
-		if (offset < BUFFER_SIZE)
-			block_size = offset;
-
-		/* Start of current block */
-		offset -= block_size;
+		int block_size = BUFFER_SIZE;
 
 		lseek(f->fd, offset, SEEK_SET);
 
@@ -168,21 +165,30 @@ static off_t lines_to_offset(struct file_struct *f, unsigned int n_lines)
 			return -1;
 		}
 
-		for (i = block_size; i > 0; i--) {
+		for (i = 0; i < block_size; i++) {
 			if (buf[i] == '\n') {
 				n_lines--;
-
 				if (n_lines == 0) {
-					offset += i + 1; /* We don't want the first \n */
-					break;
+					offset += i + 1;
+					return offset;
 				}
 			}
 		}
+
+		offset += block_size;
 	}
 
 	return offset;
 }
 
+static off_t lines_to_offset(struct file_struct *f, unsigned int n_lines)
+{
+	if (from_begin)
+		return lines_to_offset_from_begin(f, n_lines);
+	else
+		return lines_to_offset_from_end(f, n_lines);
+}
+
 static inline off_t bytes_to_offset(struct file_struct *f, unsigned int n_bytes)
 {
 	/* tail everything for 'inotail -c +0' */