diff options
| -rw-r--r-- | inotail.c | 139 |
1 files changed, 131 insertions, 8 deletions
@@ -31,6 +31,7 @@ #include <errno.h> #include <getopt.h> #include <ctype.h> +#include <assert.h> #include <sys/types.h> #include <sys/stat.h> @@ -64,6 +65,18 @@ static const struct option long_opts[] = { { NULL, 0, NULL, 0 } }; +static char *emalloc(size_t size) +{ + char *ret = malloc(size); + + if (unlikely(!ret)) { + fprintf(stderr, "Error: Failed to allocate %d bytes of memory (%s)\n", size, strerror(errno)); + exit(EXIT_FAILURE); + } + + return ret; +} + static void usage(const int status) { fprintf(stdout, "Usage: %s [OPTION]... [FILE]...\n\n" @@ -218,8 +231,123 @@ static off_t bytes_to_offset(struct file_struct *f, unsigned long n_bytes) return offset; } +/* For now more or less a copy of pipe_lines() from coreutils tail */ static ssize_t tail_pipe_lines(struct file_struct *f, unsigned long n_lines) { + struct line_buf { + char buf[BUFFER_SIZE]; + size_t n_lines; + size_t n_bytes; + struct line_buf *next; + }; + struct line_buf *first, *last, *tmp; + ssize_t rc; + unsigned long total_lines = 0; + + dprintf("in tail_pipe_lines (%d)\n"); + + if (n_lines == 0) + return 0; + + first = last = emalloc(sizeof(struct line_buf)); + first->n_bytes = first->n_lines = 0; + first->next = NULL; + tmp = emalloc(sizeof(struct line_buf)); + + while (1) { + const char *p; + + if ((rc = read(f->fd, tmp->buf, BUFFER_SIZE)) <= 0) + break; + tmp->n_bytes = rc; + tmp->n_lines = 0; + tmp->next = NULL; + p = tmp->buf; + + /* Count the lines in the current buffer */ + while ((p = memchr(p, '\n', tmp->buf + rc - p))) { + ++p; + ++tmp->n_lines; + } + total_lines += tmp->n_lines; + + /* Try to append to the previous buffer if there's enough free + * space + */ + if (tmp->n_bytes + last->n_bytes < BUFFER_SIZE) { + memcpy(&last->buf[last->n_bytes], tmp->buf, tmp->n_bytes); + last->n_bytes += tmp->n_bytes; + last->n_lines += tmp->n_lines; + } else { + last = last->next = tmp; + if (total_lines - first->n_lines > n_lines) { + tmp = first; + total_lines -= first->n_lines; + first = first->next; + } else + tmp = emalloc(sizeof(struct line_buf)); + } + } + + free(tmp); + + /* XXX: Even necessary? */ + if (rc < 0) { + fprintf(stderr, "Error: Could not read from %s\n", pretty_name(f->name)); + rc = -1; + goto err_out; + } + + if (last->n_bytes == 0) + goto err_out; + + /* Count incomplete lines */ + if (last->buf[last->n_bytes - 1] != '\n') { + ++last->n_lines; + ++total_lines; + } + + /* Skip unneeded buffers */ + for (tmp = first; total_lines - tmp->n_lines > n_lines; tmp = tmp->next) + total_lines -= tmp->n_lines; + + { + char const *p = tmp->buf; + if (total_lines > n_lines) { + size_t j; + for (j = total_lines - n_lines; j; --j) { + p = memchr(p, '\n', tmp->buf + tmp->n_bytes - p); + assert(p); + ++p; + } + } + + write(STDOUT_FILENO, p, tmp->buf + tmp->n_bytes - p); + } + + for (tmp = tmp->next; tmp; tmp = tmp->next) + if (write(STDOUT_FILENO, tmp->buf, tmp->n_bytes) <= 0) { + /* e.g. when writing to a pipe which gets closed */ + fprintf(stderr, "Error: Could not write to stdout (%s)\n", strerror(errno)); + rc = -1; + break; + } + + rc = 0; + +err_out: + while (first) { + tmp = first->next; + free(first); + first = tmp; + } + + return rc; +} + +/* TODO: Implement me :) */ +static ssize_t tail_pipe_bytes(struct file_struct *f, unsigned long n_bytes) +{ ssize_t rc; char buf[BUFFER_SIZE]; @@ -234,11 +362,6 @@ static ssize_t tail_pipe_lines(struct file_struct *f, unsigned long n_lines) return rc; } -static ssize_t tail_pipe_bytes(struct file_struct *f, unsigned long n_bytes) { - /* TODO: Implement me :) */ - return 0; -} - static int tail_file(struct file_struct *f, unsigned long n_units, char mode, char forever) { ssize_t bytes_read = 0; @@ -293,14 +416,14 @@ static int tail_file(struct file_struct *f, unsigned long n_units, char mode, ch return -1; } - if (verbose) - write_header(f->name); - if (lseek(f->fd, offset, SEEK_SET) == (off_t) -1) { fprintf(stderr, "Error: Could not seek in file '%s' (%s)\n", f->name, strerror(errno)); return -1; } + if (verbose) + write_header(f->name); + while ((bytes_read = read(f->fd, buf, BUFFER_SIZE)) > 0) write(STDOUT_FILENO, buf, (size_t) bytes_read); |