diff options
Diffstat (limited to 'src/head.c')
| -rw-r--r-- | src/head.c | 147 |
1 files changed, 87 insertions, 60 deletions
diff --git a/src/head.c b/src/head.c index d2f1fce60..2782f8e8c 100644 --- a/src/head.c +++ b/src/head.c @@ -36,6 +36,7 @@ #include "quote.h" #include "quotearg.h" #include "safe-read.h" +#include "stat-size.h" #include "xfreopen.h" #include "xstrtol.h" @@ -206,13 +207,42 @@ copy_fd (int src_fd, uintmax_t n_bytes) return COPY_FD_OK; } -/* Print all but the last N_ELIDE bytes from the input available via - the non-seekable file descriptor FD. Return true upon success. +/* Call lseek (FD, OFFSET, WHENCE), where file descriptor FD + corresponds to the file FILENAME. WHENCE must be SEEK_SET or + SEEK_CUR. Return the resulting offset. Give a diagnostic and + return -1 if lseek fails. */ + +static off_t +elseek (int fd, off_t offset, int whence, char const *filename) +{ + off_t new_offset = lseek (fd, offset, whence); + char buf[INT_BUFSIZE_BOUND (offset)]; + + if (new_offset < 0) + error (0, errno, + _(whence == SEEK_SET + ? N_("%s: cannot seek to offset %s") + : N_("%s: cannot seek to relative offset %s")), + quotearg_colon (filename), + offtostr (offset, buf)); + + return new_offset; +} + +/* For an input file with name FILENAME and descriptor FD, + output all but the last N_ELIDE_0 bytes. + If CURRENT_POS is nonnegative, assume that the input file is + positioned at CURRENT_POS and that it should be repositioned to + just before the elided bytes before returning. + Return true upon success. Give a diagnostic and return false upon error. */ static bool -elide_tail_bytes_pipe (const char *filename, int fd, uintmax_t n_elide_0) +elide_tail_bytes_pipe (const char *filename, int fd, uintmax_t n_elide_0, + off_t current_pos) { size_t n_elide = n_elide_0; + uintmax_t desired_pos = current_pos; + bool ok = true; #ifndef HEAD_TAIL_PIPE_READ_BUFSIZE # define HEAD_TAIL_PIPE_READ_BUFSIZE BUFSIZ @@ -251,7 +281,6 @@ elide_tail_bytes_pipe (const char *filename, int fd, uintmax_t n_elide_0) if (n_elide <= HEAD_TAIL_PIPE_BYTECOUNT_THRESHOLD) { - bool ok = true; bool first = true; bool eof = false; size_t n_to_read = READ_BUFSIZE + n_elide; @@ -293,22 +322,26 @@ elide_tail_bytes_pipe (const char *filename, int fd, uintmax_t n_elide_0) /* Output any (but maybe just part of the) elided data from the previous round. */ if (! first) - xwrite_stdout (b[!i] + READ_BUFSIZE, n_elide - delta); + { + desired_pos += n_elide - delta; + xwrite_stdout (b[!i] + READ_BUFSIZE, n_elide - delta); + } first = false; if (n_elide < n_read) - xwrite_stdout (b[i], n_read - n_elide); + { + desired_pos += n_read - n_elide; + xwrite_stdout (b[i], n_read - n_elide); + } } free (b[0]); - return ok; } else { /* Read blocks of size READ_BUFSIZE, until we've read at least n_elide bytes. Then, for each new buffer we read, also write an old one. */ - bool ok = true; bool eof = false; size_t n_read; bool buffered_enough; @@ -357,7 +390,10 @@ elide_tail_bytes_pipe (const char *filename, int fd, uintmax_t n_elide_0) buffered_enough = true; if (buffered_enough) - xwrite_stdout (b[i_next], n_read); + { + desired_pos += n_read; + xwrite_stdout (b[i_next], n_read); + } } /* Output any remainder: rem bytes from b[i] + n_read. */ @@ -366,6 +402,7 @@ elide_tail_bytes_pipe (const char *filename, int fd, uintmax_t n_elide_0) if (buffered_enough) { size_t n_bytes_left_in_b_i = READ_BUFSIZE - n_read; + desired_pos += rem; if (rem < n_bytes_left_in_b_i) { xwrite_stdout (b[i] + n_read, rem); @@ -392,6 +429,7 @@ elide_tail_bytes_pipe (const char *filename, int fd, uintmax_t n_elide_0) */ size_t y = READ_BUFSIZE - rem; size_t x = n_read - y; + desired_pos += x; xwrite_stdout (b[i_next], x); } } @@ -400,36 +438,16 @@ elide_tail_bytes_pipe (const char *filename, int fd, uintmax_t n_elide_0) for (i = 0; i < n_alloc; i++) free (b[i]); free (b); - - return ok; } -} - -/* Call lseek (FD, OFFSET, WHENCE), where file descriptor FD - corresponds to the file FILENAME. WHENCE must be SEEK_SET or - SEEK_CUR. Return the resulting offset. Give a diagnostic and - return -1 if lseek fails. */ - -static off_t -elseek (int fd, off_t offset, int whence, char const *filename) -{ - off_t new_offset = lseek (fd, offset, whence); - char buf[INT_BUFSIZE_BOUND (offset)]; - if (new_offset < 0) - error (0, errno, - _(whence == SEEK_SET - ? N_("%s: cannot seek to offset %s") - : N_("%s: cannot seek to relative offset %s")), - quotearg_colon (filename), - offtostr (offset, buf)); - - return new_offset; + if (0 <= current_pos && elseek (fd, desired_pos, SEEK_SET, filename) < 0) + ok = false; + return ok; } /* For the file FILENAME with descriptor FD, output all but the last N_ELIDE bytes. If SIZE is nonnegative, this is a regular file positioned - at START_POS with SIZE bytes. Return true on success. + at CURRENT_POS with SIZE bytes. Return true on success. Give a diagnostic and return false upon error. */ /* NOTE: if the input file shrinks by more than N_ELIDE bytes between @@ -437,10 +455,11 @@ elseek (int fd, off_t offset, int whence, char const *filename) static bool elide_tail_bytes_file (const char *filename, int fd, uintmax_t n_elide, - off_t current_pos, off_t size) + struct stat const *st, off_t current_pos) { - if (size < 0) - return elide_tail_bytes_pipe (filename, fd, n_elide); + off_t size = st->st_size; + if (size <= ST_BLKSIZE (*st)) + return elide_tail_bytes_pipe (filename, fd, n_elide, current_pos); else { /* Be careful here. The current position may actually be @@ -460,13 +479,16 @@ elide_tail_bytes_file (const char *filename, int fd, uintmax_t n_elide, } } -/* Print all but the last N_ELIDE lines from the input stream - open for reading via file descriptor FD. +/* For an input file with name FILENAME and descriptor FD, + output all but the last N_ELIDE_0 bytes. + If CURRENT_POS is nonnegative, the input file is positioned there + and should be repositioned to just before the elided bytes. Buffer the specified number of lines as a linked list of LBUFFERs, adding them as needed. Return true if successful. */ static bool -elide_tail_lines_pipe (const char *filename, int fd, uintmax_t n_elide) +elide_tail_lines_pipe (const char *filename, int fd, uintmax_t n_elide, + off_t current_pos) { struct linebuffer { @@ -475,6 +497,7 @@ elide_tail_lines_pipe (const char *filename, int fd, uintmax_t n_elide) size_t nlines; struct linebuffer *next; }; + uintmax_t desired_pos = current_pos; typedef struct linebuffer LBUFFER; LBUFFER *first, *last, *tmp; size_t total_lines = 0; /* Total number of newlines in all buffers. */ @@ -497,6 +520,7 @@ elide_tail_lines_pipe (const char *filename, int fd, uintmax_t n_elide) if (! n_elide) { + desired_pos += n_read; xwrite_stdout (tmp->buffer, n_read); continue; } @@ -536,6 +560,7 @@ elide_tail_lines_pipe (const char *filename, int fd, uintmax_t n_elide) last = last->next = tmp; if (n_elide < total_lines - first->nlines) { + desired_pos += first->nbytes; xwrite_stdout (first->buffer, first->nbytes); tmp = first; total_lines -= first->nlines; @@ -565,6 +590,7 @@ elide_tail_lines_pipe (const char *filename, int fd, uintmax_t n_elide) for (tmp = first; n_elide < total_lines - tmp->nlines; tmp = tmp->next) { + desired_pos += tmp->nbytes; xwrite_stdout (tmp->buffer, tmp->nbytes); total_lines -= tmp->nlines; } @@ -581,6 +607,7 @@ elide_tail_lines_pipe (const char *filename, int fd, uintmax_t n_elide) ++tmp->nlines; --n; } + desired_pos += p - tmp->buffer; xwrite_stdout (tmp->buffer, p - tmp->buffer); } @@ -591,6 +618,9 @@ free_lbuffers: free (first); first = tmp; } + + if (0 <= current_pos && elseek (fd, desired_pos, SEEK_SET, filename) < 0) + ok = false; return ok; } @@ -714,10 +744,11 @@ elide_tail_lines_seekable (const char *pretty_filename, int fd, static bool elide_tail_lines_file (const char *filename, int fd, uintmax_t n_elide, - off_t current_pos, off_t size) + struct stat const *st, off_t current_pos) { - if (size < 0) - return elide_tail_lines_pipe (filename, fd, n_elide); + off_t size = st->st_size; + if (size <= ST_BLKSIZE (*st)) + return elide_tail_lines_pipe (filename, fd, n_elide, current_pos); else { /* Find the offset, OFF, of the Nth newline from the end, @@ -802,28 +833,24 @@ head (const char *filename, int fd, uintmax_t n_units, bool count_lines, if (elide_from_end) { - off_t current_pos = -1, size = -1; - if (! presume_input_pipe) + off_t current_pos = -1; + struct stat st; + if (fstat (fd, &st) != 0) { - struct stat st; - if (fstat (fd, &st) != 0) - { - error (0, errno, _("cannot fstat %s"), - quotearg_colon (filename)); - return false; - } - if (S_ISREG (st.st_mode)) - { - size = st.st_size; - current_pos = elseek (fd, 0, SEEK_CUR, filename); - if (current_pos < 0) - return false; - } + error (0, errno, _("cannot fstat %s"), + quotearg_colon (filename)); + return false; + } + if (! presume_input_pipe && usable_st_size (&st)) + { + current_pos = elseek (fd, 0, SEEK_CUR, filename); + if (current_pos < 0) + return false; } if (count_lines) - return elide_tail_lines_file (filename, fd, n_units, current_pos, size); + return elide_tail_lines_file (filename, fd, n_units, &st, current_pos); else - return elide_tail_bytes_file (filename, fd, n_units, current_pos, size); + return elide_tail_bytes_file (filename, fd, n_units, &st, current_pos); } if (count_lines) return head_lines (filename, fd, n_units); |