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Explain a subtle API change that was made recently.

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Even though I believe this is a good change, it does
have the potential to break certain clients, so it's
good to document the reasoning behind the change.
This commit is contained in:
Tim Kientzle 2008-01-23 05:47:08 +00:00
parent 1466a90ac6
commit 991a64e41e
1 changed files with 21 additions and 0 deletions
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21
lib/libarchive/test/test_write_disk.c
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@ -60,6 +60,23 @@ static void create_reg_file(struct archive_entry *ae, const char *msg)
/* Write the entry to disk. */
assert((ad = archive_write_disk_new()) != NULL);
failure("%s", msg);
/*
* A touchy API design issue: archive_write_data() does (as of
* 2.4.12) enforce the entry size as a limit on the data
* written to the file. This was not enforced prior to
* 2.4.12. The change was prompted by the refined
* hardlink-restore semantics introduced at that time. In
* short, libarchive needs to know whether a "hardlink entry"
* is going to overwrite the contents so that it can know
* whether or not to open the file for writing. This implies
* that there is a fundamental semantic difference between an
* entry with a zero size and one with a non-zero size in the
* case of hardlinks and treating the hardlink case
* differently from the regular file case is just asking for
* trouble. So, a zero size must always mean that no data
* will be accepted, which is consistent with the file size in
* the entry being a maximum size.
*/
archive_entry_set_size(ae, sizeof(data));
assertEqualIntA(ad, 0, archive_write_header(ad, ae));
assertEqualInt(sizeof(data), archive_write_data(ad, data, sizeof(data)));
@ -93,6 +110,10 @@ static void create_reg_file2(struct archive_entry *ae, const char *msg)
/* Write the entry to disk. */
assert((ad = archive_write_disk_new()) != NULL);
failure("%s", msg);
/*
* See above for an explanation why this next call
* is necessary.
*/
archive_entry_set_size(ae, datasize);
assertEqualIntA(ad, 0, archive_write_header(ad, ae));
for (i = 0; i < datasize - 999; i += 1000) {