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Diffstat (limited to 'libmailutils/stream/streamshift.c')
| -rw-r--r-- | libmailutils/stream/streamshift.c | 279 |
1 files changed, 279 insertions, 0 deletions
diff --git a/libmailutils/stream/streamshift.c b/libmailutils/stream/streamshift.c new file mode 100644 index 000000000..cf7f35b25 --- /dev/null +++ b/libmailutils/stream/streamshift.c @@ -0,0 +1,279 @@ +/* GNU Mailutils -- a suite of utilities for electronic mail + Copyright (C) 2020-2024 Free Software Foundation, Inc. + + This library is free software; you can redistribute it and/or modify + it under the terms of the GNU Lesser General Public License as published by + the Free Software Foundation; either version 3, or (at your option) + any later version. + + This library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with GNU Mailutils. If not, see <http://www.gnu.org/licenses/>. */ + +/* + * This file implements a generic function for shifting file contents + * in place. + */ + +#include <config.h> +#include <stdlib.h> +#include <string.h> +#include <errno.h> +#include <mailutils/types.h> +#include <mailutils/stream.h> +#include <mailutils/diag.h> + +/* Shift contents of the stream starting at OFF_B to OFF_A */ +static int +stream_shift_up (mu_stream_t str, mu_off_t off_a, mu_off_t off_b, + size_t bufsize) +{ + int rc; + char *buffer = NULL; + mu_off_t length; + + /* Eliminate obvious cases: */ + + /* 1. Negative offsets */ + if (off_a < 0 || off_b < 0) + return EINVAL; + + /* 2. Offsets out of order. */ + if (off_b < off_a) + return EINVAL; + + /* 3. Offsets are equal. Nothing to do. */ + if (off_b == off_a) + return 0; + + rc = mu_stream_size (str, &length); + if (rc) + { + mu_diag_funcall (MU_DIAG_ERROR, "mu_stream_size", NULL, rc); + return rc; + } + + /* 4. Offsets out of range. */ + if (off_a > length || off_b > length) + return EINVAL; + + /* 5. Shift starting past the last byte: Nothing to do */ + if (off_b == length) + return 0; + + /* Do the actual shift. */ + + /* Select the buffer size */ + if (bufsize == 0) + /* Try to shift in one go. */ + bufsize = length - off_b; + + /* Allocate the buffer */ + while (bufsize) + { + buffer = malloc (bufsize); + if (buffer) + break; + bufsize /= 2; + } + if (!buffer) + return ENOMEM; + + /* Shift */ + while (1) + { + size_t n; + + rc = mu_stream_seek (str, off_b, MU_SEEK_SET, NULL); + if (rc) + { + mu_diag_funcall(MU_DIAG_ERROR, "mu_stream_seek", NULL, rc); + break; + } + + rc = mu_stream_read (str, buffer, bufsize, &n); + if (rc) + { + mu_diag_funcall (MU_DIAG_ERROR, "mu_stream_read", NULL, rc); + break; + } + + if (n == 0) + break; + + off_b += n; + + rc = mu_stream_seek (str, off_a, MU_SEEK_SET, NULL); + if (rc) + { + mu_diag_funcall(MU_DIAG_ERROR, "mu_stream_seek", NULL, rc); + break; + } + + rc = mu_stream_write (str, buffer, n, NULL); + if (rc) + { + mu_diag_funcall(MU_DIAG_ERROR, "mu_stream_write", NULL, rc); + break; + } + off_a += n; + } + + if (rc == 0) + { + rc = mu_stream_truncate (str, off_a); + if (rc) + mu_diag_funcall(MU_DIAG_ERROR, "mu_stream_truncate", NULL, rc); + } + + free (buffer); + return rc; +} + +/* Shift contents of the stream starting at OFF_A to OFF_B */ +static int +stream_shift_down (mu_stream_t str, mu_off_t off_a, mu_off_t off_b, + size_t bufsize) +{ + int rc; + char *buffer = NULL; + mu_off_t length; + mu_off_t nshift; + + /* Eliminate obvious cases */ + + /* 1. Negative offsets */ + if (off_a < 0 || off_b < 0) + return EINVAL; + + /* 2. Offsets out of order. */ + if (off_b < off_a) + return EINVAL; + + /* 3. Offsets are equal. Nothing to do. */ + if (off_b == off_a) + return 0; + + rc = mu_stream_size (str, &length); + if (rc) + { + mu_diag_funcall (MU_DIAG_ERROR, "mu_stream_size", NULL, rc); + return rc; + } + + /* 4. Offsets out of range. */ + if (off_a > length || off_b > length) + return EINVAL; + + /* Do the actual shift. */ + + /* Select the buffer size */ + if (bufsize == 0 || bufsize > length - off_b) + /* Try to shift in one go. */ + bufsize = length - off_a; + + /* Allocate the buffer */ + while (bufsize) + { + buffer = malloc (bufsize); + if (buffer) + break; + bufsize /= 2; + } + if (!buffer) + return ENOMEM; + + nshift = off_b - off_a; + off_b = length; + + /* Shift */ + + do + { + size_t n; + + if (off_b - off_a >= bufsize) + { + n = bufsize; + } + else + { + n = off_b - off_a; + } + + off_b -= n; + rc = mu_stream_seek (str, off_b, MU_SEEK_SET, NULL); + if (rc) + { + mu_diag_funcall(MU_DIAG_ERROR, "mu_stream_seek", NULL, rc); + break; + } + + rc = mu_stream_read (str, buffer, n, NULL); + if (rc) + { + mu_diag_funcall (MU_DIAG_ERROR, "mu_stream_read", NULL, rc); + break; + } + + rc = mu_stream_seek (str, nshift - (mu_off_t)n, MU_SEEK_CUR, NULL); + if (rc) + { + mu_diag_funcall (MU_DIAG_ERROR, "mu_stream_seek", NULL, rc); + break; + } + rc = mu_stream_write (str, buffer, n, NULL); + if (rc) + { + mu_diag_funcall (MU_DIAG_ERROR, "mu_stream_write", NULL, rc); + break; + } + mu_stream_flush (str); + } + while (off_a < off_b); + + free (buffer); + return rc; +} + +/* Shift contents of the stream starting at OFF_B to OFF_A */ +int +mu_stream_shift (mu_stream_t str, mu_off_t off_a, mu_off_t off_b, + size_t bufsize) +{ + mu_off_t needle, size; + int rc; + + /* Save current position for restoring it later. */ + rc = mu_stream_seek (str, 0, MU_SEEK_CUR, &needle); + if (rc) + { + mu_diag_funcall (MU_DIAG_ERROR, "mu_stream_seek", NULL, rc); + return rc; + } + + /* Do the actual job.*/ + if (off_b > off_a) + rc = stream_shift_up (str, off_a, off_b, bufsize); + else + rc = stream_shift_down (str, off_b, off_a, bufsize); + + if (rc == 0) + { + /* Restore the stream position on success. + If old position is greater than the actual stream size, leave + the stream pointer where it is (i.e. at end). + */ + rc = mu_stream_seek (str, 0, MU_SEEK_END, &size); + if (rc == 0 && needle < size) + { + rc = mu_stream_seek (str, needle, MU_SEEK_SET, NULL); + } + } + + return rc; +} |