diff options
Diffstat (limited to 'util-src/pposix.c')
| -rw-r--r-- | util-src/pposix.c | 65 |
1 files changed, 64 insertions, 1 deletions
diff --git a/util-src/pposix.c b/util-src/pposix.c index 4b4552f5..a68aa89d 100644 --- a/util-src/pposix.c +++ b/util-src/pposix.c @@ -13,7 +13,7 @@ * POSIX support functions for Lua */ -#define MODULE_VERSION "0.3.6" +#define MODULE_VERSION "0.3.7" #if defined(__linux__) @@ -788,6 +788,68 @@ int lc_fallocate(lua_State *L) { } } +/* + * Append some data to a file handle + * Attempt to allocate space first + * Truncate to original size on failure + */ +int lc_atomic_append(lua_State *L) { + int err; + size_t len; + + FILE *f = *(FILE **) luaL_checkudata(L, 1, LUA_FILEHANDLE); + const char *data = luaL_checklstring(L, 2, &len); + + off_t offset = ftell(f); + +#if defined(__linux__) + /* Try to allocate space without changing the file size. */ + if((err = fallocate(fileno(f), FALLOC_FL_KEEP_SIZE, offset, len))) { + if(errno != 0) { + /* Some old versions of Linux apparently use the return value instead of errno */ + err = errno; + } + switch(err) { + case ENOSYS: /* Kernel doesn't implement fallocate */ + case EOPNOTSUPP: /* Filesystem doesn't support it */ + /* Ignore and proceed to try to write */ + break; + + case ENOSPC: /* No space left */ + default: /* Other issues */ + lua_pushnil(L); + lua_pushstring(L, strerror(err)); + lua_pushinteger(L, err); + return 3; + } + } +#endif + + if(fwrite(data, sizeof(char), len, f) == len) { + if(fflush(f) == 0) { + lua_pushboolean(L, 1); /* Great success! */ + return 1; + } else { + err = errno; + } + } else { + err = ferror(f); + } + + fseek(f, offset, SEEK_SET); + + /* Cut partially written data */ + if(ftruncate(fileno(f), offset)) { + /* The file is now most likely corrupted, throw hard error */ + return luaL_error(L, "atomic_append() failed in ftruncate(): %s", strerror(errno)); + } + + lua_pushnil(L); + lua_pushstring(L, strerror(err)); + lua_pushinteger(L, err); + return 3; +} + /* Register functions */ int luaopen_util_pposix(lua_State *L) { @@ -828,6 +890,7 @@ int luaopen_util_pposix(lua_State *L) { #endif { "fallocate", lc_fallocate }, + { "atomic_append", lc_atomic_append }, { NULL, NULL } }; |