#include <errno.h>
#include <fcntl.h>
#include <arpa/inet.h>
+#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#define FS_NOCOW_FL 0
#endif
+
+typedef unsigned char byte;
+
static int istty2 = 0;
#endif // not __WIN32__ or __CYGWIN__
-static unsigned long long count_leading_zeros(const unsigned char * const buf,
- unsigned long long len)
-{
- const unsigned char *cur = buf;
- while(len-- && *cur == 0)
- cur++;
- return cur - buf;
-}
-
-
static int write_all(int fd, const void *buf, const size_t count)
{
size_t written = 0;
return 1;
}
+
static PyObject *append_sparse_region(const int fd, unsigned long long n)
{
- while(n)
+ while (n)
{
off_t new_off;
if (!INTEGRAL_ASSIGNMENT_FITS(&new_off, n))
}
+static PyObject *record_sparse_zeros(unsigned long long *new_pending,
+ const int fd,
+ unsigned long long prev_pending,
+ const unsigned long long count)
+{
+ // Add count additional sparse zeros to prev_pending and store the
+ // result in new_pending, or if the total won't fit in
+ // new_pending, write some of the zeros to fd sparsely, and store
+ // the remaining sum in new_pending.
+ if (!uadd(new_pending, prev_pending, count))
+ {
+ PyObject *err = append_sparse_region(fd, prev_pending);
+ if (err != NULL)
+ return err;
+ *new_pending = count;
+ }
+ return NULL;
+}
+
+
+static const byte * find_not_zero(const byte * const start,
+ const byte * const end)
+{
+ // Return a pointer to first non-zero byte between start and end,
+ // or end if there isn't one.
+ assert(start <= end);
+ const unsigned char *cur = start;
+ while (cur < end && *cur == 0)
+ cur++;
+ return cur;
+}
+
+
+static const byte * const find_trailing_zeros(const byte * const start,
+ const byte * const end)
+{
+ // Return a pointer to the start of any trailing run of zeros, or
+ // end if there isn't one.
+ assert(start <= end);
+ if (start == end)
+ return end;
+ const byte * cur = end;
+ while (cur > start && *--cur == 0) {}
+ if (*cur == 0)
+ return cur;
+ else
+ return cur + 1;
+}
+
+
+static const byte *find_non_sparse_end(const byte * const start,
+ const byte * const end,
+ const unsigned long long min_len)
+{
+ // Return the first pointer to a min_len sparse block in [start,
+ // end) if there is one, otherwise a pointer to the start of any
+ // trailing run of zeros. If there are no trailing zeros, return
+ // end.
+ if (start == end)
+ return end;
+ assert(start < end);
+ assert(min_len);
+ // Probe in min_len jumps, searching backward from the jump
+ // destination for a non-zero byte. If such a byte is found, move
+ // just past it and try again.
+ const byte *candidate = start;
+ // End of any run of zeros, starting at candidate, that we've already seen
+ const byte *end_of_known_zeros = candidate;
+ while (end - candidate >= min_len) // Handle all min_len candidate blocks
+ {
+ const byte * const probe_end = candidate + min_len;
+ const byte * const trailing_zeros =
+ find_trailing_zeros(end_of_known_zeros, probe_end);
+ if (trailing_zeros == probe_end)
+ end_of_known_zeros = candidate = probe_end;
+ else if (trailing_zeros == end_of_known_zeros)
+ {
+ assert(candidate >= start);
+ assert(candidate <= end);
+ assert(*candidate == 0);
+ return candidate;
+ }
+ else
+ {
+ candidate = trailing_zeros;
+ end_of_known_zeros = probe_end;
+ }
+ }
+
+ if (candidate == end)
+ return end;
+
+ // No min_len sparse run found, search backward from end
+ const byte * const trailing_zeros = find_trailing_zeros(end_of_known_zeros,
+ end);
+
+ if (trailing_zeros == end_of_known_zeros)
+ {
+ assert(candidate >= start);
+ assert(candidate < end);
+ assert(*candidate == 0);
+ assert(end - candidate < min_len);
+ return candidate;
+ }
+
+ if (trailing_zeros == end)
+ {
+ assert(*(end - 1) != 0);
+ return end;
+ }
+
+ assert(end - trailing_zeros < min_len);
+ assert(trailing_zeros >= start);
+ assert(trailing_zeros < end);
+ assert(*trailing_zeros == 0);
+ return trailing_zeros;
+}
+
+
static PyObject *bup_write_sparsely(PyObject *self, PyObject *args)
{
int fd;
if (!INTEGRAL_ASSIGNMENT_FITS(&buf_len, sbuf_len))
return PyErr_Format(PyExc_OverflowError, "buffer length too large");
- // The value of zeros_read indicates the number of zeros read from
- // buf that haven't been accounted for yet (with respect to cur),
- // while zeros indicates the total number of pending zeros, which
- // could be larger in the first iteration if prev_sparse_len
- // wasn't zero.
- int rc;
- unsigned long long unexamined = buf_len;
- unsigned char *block_start = buf, *cur = buf;
- unsigned long long zeros, zeros_read = count_leading_zeros(cur, unexamined);
- assert(zeros_read <= unexamined);
- unexamined -= zeros_read;
- if (!uadd(&zeros, prev_sparse_len, zeros_read))
+ const byte * block = buf; // Start of pending block
+ const byte * const end = buf + buf_len;
+ unsigned long long zeros = prev_sparse_len;
+ while (1)
{
- PyObject *err = append_sparse_region(fd, prev_sparse_len);
- if (err != NULL)
- return err;
- zeros = zeros_read;
- }
+ assert(block <= end);
+ if (block == end)
+ return PyLong_FromUnsignedLongLong(zeros);
- while(unexamined)
- {
- if (zeros < min_sparse_len)
- cur += zeros_read;
- else
+ if (*block != 0)
{
- rc = write_all(fd, block_start, cur - block_start);
- if (rc)
- return PyErr_SetFromErrno(PyExc_IOError);
+ // Look for the end of block, i.e. the next sparse run of
+ // at least min_sparse_len zeros, or the end of the
+ // buffer.
+ const byte * const probe = find_non_sparse_end(block + 1, end,
+ min_sparse_len);
+ // Either at end of block, or end of non-sparse; write pending data
PyObject *err = append_sparse_region(fd, zeros);
if (err != NULL)
return err;
- cur += zeros_read;
- block_start = cur;
- }
- // Pending zeros have ether been made sparse, or are going to
- // be rolled into the next non-sparse block since we know we
- // now have at least one unexamined non-zero byte.
- assert(unexamined && *cur != 0);
- zeros = zeros_read = 0;
- while (unexamined && *cur != 0)
- {
- cur++; unexamined--;
+ int rc = write_all(fd, block, probe - block);
+ if (rc)
+ return PyErr_SetFromErrno(PyExc_IOError);
+
+ if (end - probe < min_sparse_len)
+ zeros = end - probe;
+ else
+ zeros = min_sparse_len;
+ block = probe + zeros;
}
- if (unexamined)
+ else // *block == 0
{
- zeros_read = count_leading_zeros(cur, unexamined);
- assert(zeros_read <= unexamined);
- unexamined -= zeros_read;
- zeros = zeros_read;
+ // Should be in the first loop iteration, a sparse run of
+ // zeros, or nearly at the end of the block (within
+ // min_sparse_len).
+ const byte * const zeros_end = find_not_zero(block, end);
+ PyObject *err = record_sparse_zeros(&zeros, fd,
+ zeros, zeros_end - block);
+ if (err != NULL)
+ return err;
+ assert(block <= zeros_end);
+ block = zeros_end;
}
}
- rc = write_all(fd, block_start, cur - block_start);
- if (rc)
- return PyErr_SetFromErrno(PyExc_IOError);
- return PyLong_FromUnsignedLongLong(zeros);
}
assert(sizeof(PY_LONG_LONG) <= sizeof(long long));
assert(sizeof(unsigned PY_LONG_LONG) <= sizeof(unsigned long long));
- if (sizeof(off_t) < sizeof(int))
+ // Originally required by append_sparse_region()
{
- // Originally required by append_sparse_region().
- fprintf(stderr, "sizeof(off_t) < sizeof(int); please report.\n");
- exit(1);
+ off_t probe;
+ if (!INTEGRAL_ASSIGNMENT_FITS(&probe, INT_MAX))
+ {
+ fprintf(stderr, "off_t can't hold INT_MAX; please report.\n");
+ exit(1);
+ }
}
char *e;
projects / bup.git / commitdiff