static ERL_NIF_TERM pread_nif_impl(efile_data_t *d, ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]) {
Sint64 bytes_read, block_size, offset;
SysIOVec read_vec[1];
ErlNifBinary result;
ASSERT(argc == 2);
if(!enif_is_number(env, argv[0]) || !enif_is_number(env, argv[1])) {
return enif_make_badarg(env);
}
if(!enif_get_int64(env, argv[0], &offset) ||
!enif_get_int64(env, argv[1], &block_size) ||
(offset < 0 || block_size < 0)) {
return posix_error_to_tuple(env, EINVAL);
}
if(!enif_alloc_binary(block_size, &result)) {
return posix_error_to_tuple(env, ENOMEM);
}
read_vec[0].iov_base = result.data;
read_vec[0].iov_len = result.size;
bytes_read = efile_preadv(d, offset, read_vec, 1);
if(bytes_read < 0) {
enif_release_binary(&result);
return posix_error_to_tuple(env, d->posix_errno);
} else if(bytes_read == 0) {
enif_release_binary(&result);
return am_eof;
}
if(bytes_read < block_size && !enif_realloc_binary(&result, bytes_read)) {
ERTS_INTERNAL_ERROR("Failed to shrink pread result.");
}
return enif_make_tuple2(env, am_ok, enif_make_binary(env, &result));
}
/* This undocumented function reads a pointer and then reads the data block
* described by said pointer. It was reverse-engineered from the old
* implementation so while all tests pass it may not be entirely correct. Our
* current understanding is as follows:
*
* Pointer layout:
*
* <<Size:1/integer-unit:32, Offset:1/integer-unit:32>>
*
* Where Offset is the -absolute- address to the data block.
*
* *) If we fail to read the pointer block in its entirety, we return eof.
* *) If the provided max_payload_size is larger than Size, we return eof.
* *) If we fail to read any data whatsoever at Offset, we return
* {ok, {Size, Offset, eof}}
* *) Otherwise, we return {ok, {Size, Offset, Data}}. Note that the size
* of Data may be smaller than Size if we encounter EOF before we could
* read the entire block.
*
* On errors we'll return {error, posix()} regardless of whether they
* happened before or after reading the pointer block. */
static ERL_NIF_TERM ipread_s32bu_p32bu_nif_impl(efile_data_t *d, ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]) {
Sint64 payload_offset, payload_size;
SysIOVec read_vec[1];
Sint64 bytes_read;
ErlNifBinary payload;
if(argc != 2 || !enif_is_number(env, argv[0])
|| !enif_is_number(env, argv[1])) {
return enif_make_badarg(env);
}
{
Sint64 max_payload_size, pointer_offset;
unsigned char pointer_block[8];
if(!enif_get_int64(env, argv[0], &pointer_offset) ||
!enif_get_int64(env, argv[1], &max_payload_size) ||
(pointer_offset < 0 || max_payload_size >= 1u << 31)) {
return posix_error_to_tuple(env, EINVAL);
}
read_vec[0].iov_base = pointer_block;
read_vec[0].iov_len = sizeof(pointer_block);
bytes_read = efile_preadv(d, pointer_offset, read_vec, 1);
if(bytes_read < 0) {
return posix_error_to_tuple(env, d->posix_errno);
} else if(bytes_read < sizeof(pointer_block)) {
return am_eof;
}
payload_size = (Uint32)get_int32(&pointer_block[0]);
payload_offset = (Uint32)get_int32(&pointer_block[4]);
if(payload_size > max_payload_size) {
return am_eof;
}
}
if(!enif_alloc_binary(payload_size, &payload)) {
return posix_error_to_tuple(env, ENOMEM);
}
read_vec[0].iov_base = payload.data;
read_vec[0].iov_len = payload.size;
bytes_read = efile_preadv(d, payload_offset, read_vec, 1);
if(bytes_read < 0) {
return posix_error_to_tuple(env, d->posix_errno);
} else if(bytes_read == 0) {
enif_release_binary(&payload);
return enif_make_tuple2(env, am_ok,
enif_make_tuple3(env,
enif_make_uint(env, payload_size),
enif_make_uint(env, payload_offset),
am_eof));
}
if(bytes_read < payload.size && !enif_realloc_binary(&payload, bytes_read)) {
ERTS_INTERNAL_ERROR("Failed to shrink ipread payload.");
}
return enif_make_tuple2(env, am_ok,
enif_make_tuple3(env,
enif_make_uint(env, payload_size),
enif_make_uint(env, payload_offset),
enif_make_binary(env, &payload)));
}
