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authorDavid Oberhollenzer <david.oberhollenzer@sigma-star.at>2019-10-07 11:20:55 +0200
committerDavid Oberhollenzer <david.oberhollenzer@sigma-star.at>2019-10-07 12:22:05 +0200
commita68eb730558fb90bc8d9524564d8f9e58f3ccac1 (patch)
treede7a678b28786ec2e47e4956d8cdb0f4466f3d5c /include/sqfs/compressor.h
parentc7fdb2b305ed8b4deb67bfc6ef3257e7e6773397 (diff)
Improve ABI backward & forward compatibillity
- Padd the compressor config union - 128 bytes aught to be enough for everyone, i.e. future compressors. - Insist that the padding space is initialized to 0. If a field gets added to an existing compressor, it can test for 0 as a sentinel value. - Add a size field to the hook structure, aka "the Microsoft way". - The explanation is in the comment. - Don't make the Microsoft mistake of checking for >=, insist on *exact* size match. Future users will need a fallback if their hooks are rejected. But at least they will be rejected instead of silently not being used. - Add an unsupported flag check to the dir tree reader. - Add a basic abi unit test that, for now, checks the size of the compressor config struct fields. Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Diffstat (limited to 'include/sqfs/compressor.h')
-rw-r--r--include/sqfs/compressor.h15
1 files changed, 15 insertions, 0 deletions
diff --git a/include/sqfs/compressor.h b/include/sqfs/compressor.h
index 46bdf58..a53fbc1 100644
--- a/include/sqfs/compressor.h
+++ b/include/sqfs/compressor.h
@@ -100,6 +100,11 @@ struct sqfs_compressor_t {
* @struct sqfs_compressor_config_t
*
* @brief Configuration parameters for instantiating a compressor backend.
+ *
+ * The unused fields MUST be set to 0. The easiest way to do this is by always
+ * clearing the struct using memset before setting anything, or using
+ * @ref sqfs_compressor_config_init to set defaults and then modify the struct
+ * from there.
*/
struct sqfs_compressor_config_t {
/**
@@ -138,6 +143,8 @@ struct sqfs_compressor_config_t {
* Default is 15, i.e. 32k window.
*/
sqfs_u16 window_size;
+
+ sqfs_u32 padd0[3];
} gzip;
/**
@@ -150,6 +157,8 @@ struct sqfs_compressor_config_t {
* Default is 15.
*/
sqfs_u16 level;
+
+ sqfs_u16 padd0[7];
} zstd;
/**
@@ -174,6 +183,8 @@ struct sqfs_compressor_config_t {
* Defaults to 9, i.e. best compression.
*/
sqfs_u16 level;
+
+ sqfs_u32 padd0[3];
} lzo;
/**
@@ -190,7 +201,11 @@ struct sqfs_compressor_config_t {
* block size.
*/
sqfs_u32 dict_size;
+
+ sqfs_u32 padd0[3];
} xz;
+
+ sqfs_u64 padd0[2];
} opt;
};