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LarryRuaneLarryRuane
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util: CBufferedFile fixes
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2 files changed

+257
-11
lines changed

2 files changed

+257
-11
lines changed

‎src/streams.h

Lines changed: 13 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -735,16 +735,17 @@ class CBufferedFile
735735
size_t nBytes = fread((void*)&vchBuf[pos], 1, readNow, src);
736736
if (nBytes == 0) {
737737
throw std::ios_base::failure(feof(src) ? "CBufferedFile::Fill: end of file" : "CBufferedFile::Fill: fread failed");
738-
} else {
739-
nSrcPos += nBytes;
740-
return true;
741738
}
739+
nSrcPos += nBytes;
740+
return true;
742741
}
743742

744743
public:
745744
CBufferedFile(FILE *fileIn, uint64_t nBufSize, uint64_t nRewindIn, int nTypeIn, int nVersionIn) :
746745
nType(nTypeIn), nVersion(nVersionIn), nSrcPos(0), nReadPos(0), nReadLimit(std::numeric_limits<uint64_t>::max()), nRewind(nRewindIn), vchBuf(nBufSize, 0)
747746
{
747+
if (nRewindIn >= nBufSize)
748+
throw std::ios_base::failure("Rewind limit must be less than buffer size");
748749
src = fileIn;
749750
}
750751

@@ -777,8 +778,6 @@ class CBufferedFile
777778
void read(char *pch, size_t nSize) {
778779
if (nSize + nReadPos > nReadLimit)
779780
throw std::ios_base::failure("Read attempted past buffer limit");
780-
if (nSize + nRewind > vchBuf.size())
781-
throw std::ios_base::failure("Read larger than buffer size");
782781
while (nSize > 0) {
783782
if (nReadPos == nSrcPos)
784783
Fill();
@@ -802,16 +801,19 @@ class CBufferedFile
802801

803802
//! rewind to a given reading position
804803
bool SetPos(uint64_t nPos) {
805-
nReadPos = nPos;
806-
if (nReadPos + nRewind < nSrcPos) {
807-
nReadPos = nSrcPos - nRewind;
804+
size_t bufsize = vchBuf.size();
805+
if (nPos + bufsize < nSrcPos) {
806+
// rewinding too far, rewind as far as possible
807+
nReadPos = nSrcPos - bufsize;
808808
return false;
809-
} else if (nReadPos > nSrcPos) {
809+
}
810+
if (nPos > nSrcPos) {
811+
// can't go this far forward, go as far as possible
810812
nReadPos = nSrcPos;
811813
return false;
812-
} else {
813-
return true;
814814
}
815+
nReadPos = nPos;
816+
return true;
815817
}
816818

817819
bool Seek(uint64_t nPos) {

‎src/test/streams_tests.cpp

Lines changed: 244 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2,6 +2,7 @@
22
// Distributed under the MIT software license, see the accompanying
33
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
44

5+
#include <random.h>
56
#include <streams.h>
67
#include <test/setup_common.h>
78

@@ -202,4 +203,247 @@ BOOST_AUTO_TEST_CASE(streams_serializedata_xor)
202203
std::string(ds.begin(), ds.end()));
203204
}
204205

206+
BOOST_AUTO_TEST_CASE(streams_buffered_file)
207+
{
208+
FILE* file = fsbridge::fopen("streams_test_tmp", "w+b");
209+
// The value at each offset is the offset.
210+
for (uint8_t j = 0; j < 40; ++j) {
211+
fwrite(&j, 1, 1, file);
212+
}
213+
rewind(file);
214+
215+
// The buffer size (second arg) must be greater than the rewind
216+
// amount (third arg).
217+
try {
218+
CBufferedFile bfbad(file, 25, 25, 222, 333);
219+
BOOST_CHECK(false);
220+
} catch (const std::exception& e) {
221+
BOOST_CHECK(strstr(e.what(),
222+
"Rewind limit must be less than buffer size") != nullptr);
223+
}
224+
225+
// The buffer is 25 bytes, allow rewinding 10 bytes.
226+
CBufferedFile bf(file, 25, 10, 222, 333);
227+
BOOST_CHECK(!bf.eof());
228+
229+
// These two members have no functional effect.
230+
BOOST_CHECK_EQUAL(bf.GetType(), 222);
231+
BOOST_CHECK_EQUAL(bf.GetVersion(), 333);
232+
233+
uint8_t i;
234+
bf >> i;
235+
BOOST_CHECK_EQUAL(i, 0);
236+
bf >> i;
237+
BOOST_CHECK_EQUAL(i, 1);
238+
239+
// After reading bytes 0 and 1, we're positioned at 2.
240+
BOOST_CHECK_EQUAL(bf.GetPos(), 2);
241+
242+
// Rewind to offset 0, ok (within the 10 byte window).
243+
BOOST_CHECK(bf.SetPos(0));
244+
bf >> i;
245+
BOOST_CHECK_EQUAL(i, 0);
246+
247+
// We can go forward to where we've been, but beyond may fail.
248+
BOOST_CHECK(bf.SetPos(2));
249+
bf >> i;
250+
BOOST_CHECK_EQUAL(i, 2);
251+
252+
// If you know the maximum number of bytes that should be
253+
// read to deserialize the variable, you can limit the read
254+
// extent. The current file offset is 3, so the following
255+
// SetLimit() allows zero bytes to be read.
256+
BOOST_CHECK(bf.SetLimit(3));
257+
try {
258+
bf >> i;
259+
BOOST_CHECK(false);
260+
} catch (const std::exception& e) {
261+
BOOST_CHECK(strstr(e.what(),
262+
"Read attempted past buffer limit") != nullptr);
263+
}
264+
// The default argument removes the limit completely.
265+
BOOST_CHECK(bf.SetLimit());
266+
// The read position should still be at 3 (no change).
267+
BOOST_CHECK_EQUAL(bf.GetPos(), 3);
268+
269+
// Read from current offset, 3, forward until position 10.
270+
for (uint8_t j = 3; j < 10; ++j) {
271+
bf >> i;
272+
BOOST_CHECK_EQUAL(i, j);
273+
}
274+
BOOST_CHECK_EQUAL(bf.GetPos(), 10);
275+
276+
// We're guaranteed (just barely) to be able to rewind to zero.
277+
BOOST_CHECK(bf.SetPos(0));
278+
BOOST_CHECK_EQUAL(bf.GetPos(), 0);
279+
bf >> i;
280+
BOOST_CHECK_EQUAL(i, 0);
281+
282+
// We can set the position forward again up to the farthest
283+
// into the stream we've been, but no farther. (Attempting
284+
// to go farther may succeed, but it's not guaranteed.)
285+
BOOST_CHECK(bf.SetPos(10));
286+
bf >> i;
287+
BOOST_CHECK_EQUAL(i, 10);
288+
BOOST_CHECK_EQUAL(bf.GetPos(), 11);
289+
290+
// Now it's only guaranteed that we can rewind to offset 1
291+
// (current read position, 11, minus rewind amount, 10).
292+
BOOST_CHECK(bf.SetPos(1));
293+
BOOST_CHECK_EQUAL(bf.GetPos(), 1);
294+
bf >> i;
295+
BOOST_CHECK_EQUAL(i, 1);
296+
297+
// We can stream into large variables, even larger than
298+
// the buffer size.
299+
BOOST_CHECK(bf.SetPos(11));
300+
{
301+
uint8_t a[40 - 11];
302+
bf >> a;
303+
for (uint8_t j = 0; j < sizeof(a); ++j) {
304+
BOOST_CHECK_EQUAL(a[j], 11 + j);
305+
}
306+
}
307+
BOOST_CHECK_EQUAL(bf.GetPos(), 40);
308+
309+
// We've read the entire file, the next read should throw.
310+
try {
311+
bf >> i;
312+
BOOST_CHECK(false);
313+
} catch (const std::exception& e) {
314+
BOOST_CHECK(strstr(e.what(),
315+
"CBufferedFile::Fill: end of file") != nullptr);
316+
}
317+
// Attempting to read beyond the end sets the EOF indicator.
318+
BOOST_CHECK(bf.eof());
319+
320+
// Still at offset 40, we can go back 10, to 30.
321+
BOOST_CHECK_EQUAL(bf.GetPos(), 40);
322+
BOOST_CHECK(bf.SetPos(30));
323+
bf >> i;
324+
BOOST_CHECK_EQUAL(i, 30);
325+
BOOST_CHECK_EQUAL(bf.GetPos(), 31);
326+
327+
// We're too far to rewind to position zero.
328+
BOOST_CHECK(!bf.SetPos(0));
329+
// But we should now be positioned at least as far back as allowed
330+
// by the rewind window (relative to our farthest read position, 40).
331+
BOOST_CHECK(bf.GetPos() <= 30);
332+
333+
// We can explicitly close the file, or the destructor will do it.
334+
bf.fclose();
335+
336+
fs::remove("streams_test_tmp");
337+
}
338+
339+
BOOST_AUTO_TEST_CASE(streams_buffered_file_rand)
340+
{
341+
// Make this test deterministic.
342+
SeedInsecureRand(true);
343+
344+
for (int rep = 0; rep < 50; ++rep) {
345+
FILE* file = fsbridge::fopen("streams_test_tmp", "w+b");
346+
size_t fileSize = InsecureRandRange(256);
347+
for (uint8_t i = 0; i < fileSize; ++i) {
348+
fwrite(&i, 1, 1, file);
349+
}
350+
rewind(file);
351+
352+
size_t bufSize = InsecureRandRange(300) + 1;
353+
size_t rewindSize = InsecureRandRange(bufSize);
354+
CBufferedFile bf(file, bufSize, rewindSize, 222, 333);
355+
size_t currentPos = 0;
356+
size_t maxPos = 0;
357+
for (int step = 0; step < 100; ++step) {
358+
if (currentPos >= fileSize)
359+
break;
360+
361+
// We haven't read to the end of the file yet.
362+
BOOST_CHECK(!bf.eof());
363+
BOOST_CHECK_EQUAL(bf.GetPos(), currentPos);
364+
365+
// Pretend the file consists of a series of objects of varying
366+
// sizes; the boundaries of the objects can interact arbitrarily
367+
// with the CBufferFile's internal buffer. These first three
368+
// cases simulate objects of various sizes (1, 2, 5 bytes).
369+
switch (InsecureRandRange(5)) {
370+
case 0: {
371+
uint8_t a[1];
372+
if (currentPos + 1 > fileSize)
373+
continue;
374+
bf.SetLimit(currentPos + 1);
375+
bf >> a;
376+
for (uint8_t i = 0; i < 1; ++i) {
377+
BOOST_CHECK_EQUAL(a[i], currentPos);
378+
currentPos++;
379+
}
380+
break;
381+
}
382+
case 1: {
383+
uint8_t a[2];
384+
if (currentPos + 2 > fileSize)
385+
continue;
386+
bf.SetLimit(currentPos + 2);
387+
bf >> a;
388+
for (uint8_t i = 0; i < 2; ++i) {
389+
BOOST_CHECK_EQUAL(a[i], currentPos);
390+
currentPos++;
391+
}
392+
break;
393+
}
394+
case 2: {
395+
uint8_t a[5];
396+
if (currentPos + 5 > fileSize)
397+
continue;
398+
bf.SetLimit(currentPos + 5);
399+
bf >> a;
400+
for (uint8_t i = 0; i < 5; ++i) {
401+
BOOST_CHECK_EQUAL(a[i], currentPos);
402+
currentPos++;
403+
}
404+
break;
405+
}
406+
case 3: {
407+
// Find a byte value (that is at or ahead of the current position).
408+
size_t find = currentPos + InsecureRandRange(8);
409+
if (find >= fileSize)
410+
find = fileSize - 1;
411+
bf.FindByte(static_cast<char>(find));
412+
// The value at each offset is the offset.
413+
BOOST_CHECK_EQUAL(bf.GetPos(), find);
414+
currentPos = find;
415+
416+
bf.SetLimit(currentPos + 1);
417+
uint8_t i;
418+
bf >> i;
419+
BOOST_CHECK_EQUAL(i, currentPos);
420+
currentPos++;
421+
break;
422+
}
423+
case 4: {
424+
size_t requestPos = InsecureRandRange(maxPos + 4);
425+
bool okay = bf.SetPos(requestPos);
426+
// The new position may differ from the requested position
427+
// because we may not be able to rewind beyond the rewind
428+
// window, and we may not be able to move forward beyond the
429+
// farthest position we've reached so far.
430+
currentPos = bf.GetPos();
431+
BOOST_CHECK_EQUAL(okay, currentPos == requestPos);
432+
// Check that we can position within the rewind window.
433+
if (requestPos <= maxPos &&
434+
maxPos > rewindSize &&
435+
requestPos >= maxPos - rewindSize) {
436+
// We requested a position within the rewind window.
437+
BOOST_CHECK(okay);
438+
}
439+
break;
440+
}
441+
}
442+
if (maxPos < currentPos)
443+
maxPos = currentPos;
444+
}
445+
}
446+
fs::remove("streams_test_tmp");
447+
}
448+
205449
BOOST_AUTO_TEST_SUITE_END()

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