diff options
Diffstat (limited to 'otherlibs')
| -rw-r--r-- | otherlibs/bigarray/mmap_unix.c | 74 |
1 files changed, 56 insertions, 18 deletions
diff --git a/otherlibs/bigarray/mmap_unix.c b/otherlibs/bigarray/mmap_unix.c index 8e71664ab..f10835443 100644 --- a/otherlibs/bigarray/mmap_unix.c +++ b/otherlibs/bigarray/mmap_unix.c @@ -25,12 +25,14 @@ extern int caml_ba_element_size[]; /* from bigarray_stubs.c */ +#include <errno.h> #ifdef HAS_UNISTD #include <unistd.h> #endif #ifdef HAS_MMAP #include <sys/types.h> #include <sys/mman.h> +#include <sys/stat.h> #endif #if defined(HAS_MMAP) @@ -39,15 +41,61 @@ extern int caml_ba_element_size[]; /* from bigarray_stubs.c */ #define MAP_FAILED ((void *) -1) #endif +/* [caml_grow_file] function contributed by Gerd Stolpmann (PR#5543). */ + +static int caml_grow_file(int fd, file_offset size) +{ + char c; + int p; + + /* First use pwrite for growing - it is a conservative method, as it + can never happen that we shrink by accident + */ +#ifdef HAS_PWRITE + c = 0; + p = pwrite(fd, &c, 1, size - 1); +#else + + /* Emulate pwrite with lseek. This should only be necessary on ancient + systems nowadays + */ + file_offset currpos; + currpos = lseek(fd, 0, SEEK_CUR); + if (currpos != -1) { + p = lseek(fd, size - 1, SEEK_SET); + if (p != -1) { + c = 0; + p = write(fd, &c, 1); + if (p != -1) + p = lseek(fd, currpos, SEEK_SET); + } + } + else p=-1; +#endif +#ifdef HAS_TRUNCATE + if (p == -1 && errno == ESPIPE) { + /* Plan B. Check if at least ftruncate is possible. There are + some non-seekable descriptor types that do not support pwrite + but ftruncate, like shared memory. We never get into this case + for real files, so there is no danger of truncating persistent + data by accident + */ + p = ftruncate(fd, size); + } +#endif + return p; +} + + CAMLprim value caml_ba_map_file(value vfd, value vkind, value vlayout, value vshared, value vdim, value vstart) { int fd, flags, major_dim, shared; intnat num_dims, i; intnat dim[CAML_BA_MAX_NUM_DIMS]; - file_offset currpos, startpos, file_size, data_size; + file_offset startpos, file_size, data_size; + struct stat st; uintnat array_size, page, delta; - char c; void * addr; fd = Int_val(vfd); @@ -65,18 +113,15 @@ CAMLprim value caml_ba_map_file(value vfd, value vkind, value vlayout, if (dim[i] < 0) caml_invalid_argument("Bigarray.create: negative dimension"); } - /* Determine file size */ + /* Determine file size. We avoid lseek here because it is fragile, + and because some mappable file types do not support it + */ caml_enter_blocking_section(); - currpos = lseek(fd, 0, SEEK_CUR); - if (currpos == -1) { - caml_leave_blocking_section(); - caml_sys_error(NO_ARG); - } - file_size = lseek(fd, 0, SEEK_END); - if (file_size == -1) { + if (fstat(fd, &st) == -1) { caml_leave_blocking_section(); caml_sys_error(NO_ARG); } + file_size = st.st_size; /* Determine array size in bytes (or size of array without the major dimension if that dimension wasn't specified) */ array_size = caml_ba_element_size[flags & CAML_BA_KIND_MASK]; @@ -99,19 +144,12 @@ CAMLprim value caml_ba_map_file(value vfd, value vkind, value vlayout, } else { /* Check that file is large enough, and grow it otherwise */ if (file_size < startpos + array_size) { - if (lseek(fd, startpos + array_size - 1, SEEK_SET) == -1) { - caml_leave_blocking_section(); - caml_sys_error(NO_ARG); - } - c = 0; - if (write(fd, &c, 1) != 1) { + if (caml_grow_file(fd, startpos + array_size) == -1) { /* PR#5543 */ caml_leave_blocking_section(); caml_sys_error(NO_ARG); } } } - /* Restore original file position */ - lseek(fd, currpos, SEEK_SET); /* Determine offset so that the mapping starts at the given file pos */ page = getpagesize(); delta = (uintnat) (startpos % page); |