disk: fix data corruption on 256-byte sector images by erichelgeson · Pull Request #362 · BlueSCSI/BlueSCSI-v2

erichelgeson · 2026-04-24T13:12:44Z

Two related bugs surfaced on images formatted with 256-byte SCSI sectors.

start_dataInTransfer() used readSectorsDirect with count >> 9 when fastseek was enabled, silently dropping the trailing 256 bytes on odd-block transfers and reading the wrong 512 bytes when the file position was not 512-aligned. Gate the direct-read path on bytesPerSector == SD_SECTOR_SIZE; 256-byte images take the regular img.file.read() path.
ImageBackingStore::read/write kept m_fsfile's position stale while serving contiguous raw-block I/O. On the first unaligned access the code flipped m_iscontiguous=false and fell back to m_fsfile still sitting at offset 0, corrupting both reads (wrong data) and writes (overwrote the image header). Sync m_fsfile from m_cursector before the mode transition in both read() and write().

Replaces #348

Two related bugs surfaced on images formatted with 256-byte SCSI sectors (fixes from PR #348, simplified): 1. start_dataInTransfer() used readSectorsDirect with count >> 9 when fastseek was enabled, silently dropping the trailing 256 bytes on odd-block transfers and reading the wrong 512 bytes when the file position was not 512-aligned. Gate the direct-read path on bytesPerSector == SD_SECTOR_SIZE; 256-byte images take the regular img.file.read() path. 2. ImageBackingStore::read/write kept m_fsfile's position stale while serving contiguous raw-block I/O. On the first unaligned access the code flipped m_iscontiguous=false and fell back to m_fsfile still sitting at offset 0, corrupting both reads (wrong data) and writes (overwrote the image header). Sync m_fsfile from m_cursector before the mode transition in both read() and write(). Co-Authored-By: Per Mårtensson <pm@sweproj.com>

github-actions · 2026-04-24T13:18:57Z

BlueSCSI Memory Report

Compared against release v2026.03.01

Memory Usage

Target	FLASH	RAM	SCRATCH_X	SCRATCH_Y
Pico_2_Audio_SPDIF	674.8 KB (+54.8 KB) [33%]	511.7 KB [100%]	3.5 KB [88%]	3.8 KB (+1.0 KB) [94%]
Pico_2_DaynaPORT	667.1 KB (+53.7 KB) [33%]	511.7 KB [100%]	3.5 KB [88%]	3.0 KB (+1.0 KB) [75%]
Pico_Audio_SPDIF	696.3 KB (+62.5 KB) [34%]	252.3 KB (+6.8 KB) [99%]	1.5 KB [38%]	768 B [19%]
Pico_DaynaPORT	688.1 KB (+61.9 KB) [34%]	246.0 KB (+15.8 KB) [96%]	1.5 KB [38%]	—
Ultra	684.1 KB (+59.1 KB) [33%]	511.7 KB [100%]	3.5 KB [88%]	3.0 KB (+1.0 KB) [75%]
Ultra_Wide	444.0 KB (+63.1 KB) [22%]	511.7 KB [100%]	2.0 KB [50%]	3.0 KB (+1.0 KB) [75%]

Symbol Region Changes

Pico_2_Audio_SPDIF: 3 symbols moved FLASH → RAM (+12 B)

Symbol	Size
`operator delete(void*, unsigned int)`	4 B
`operator new[](unsigned int)`	4 B
`operator delete[](void*)`	4 B

Pico_2_Audio_SPDIF: 9 symbols moved RAM → FLASH (-298 B RAM)

Symbol	Size
`tud_descriptor_device_cb`	116 B
`tud_descriptor_string_cb`	96 B
`_fstat`	16 B
`_lseek`	16 B
`_close`	16 B
`_isatty`	16 B
`tud_descriptor_configuration_cb`	12 B
`_read`	6 B
`_write`	4 B

Pico_2_DaynaPORT: 3 symbols moved FLASH → RAM (+12 B)

Symbol	Size
`operator delete(void*, unsigned int)`	4 B
`operator new[](unsigned int)`	4 B
`operator delete[](void*)`	4 B

Pico_2_DaynaPORT: 9 symbols moved RAM → FLASH (-298 B RAM)

Symbol	Size
`tud_descriptor_device_cb`	116 B
`tud_descriptor_string_cb`	96 B
`_fstat`	16 B
`_lseek`	16 B
`_close`	16 B
`_isatty`	16 B
`tud_descriptor_configuration_cb`	12 B
`_read`	6 B
`_write`	4 B

Pico_Audio_SPDIF: 13 symbols moved FLASH → RAM (+2.0 KB)

Symbol	Size
`mscd_xfer_cb`	1.4 KB
`mscd_control_xfer_cb`	328 B
`tud_descriptor_string_cb`	116 B
`mscd_open`	104 B
`mscd_reset`	20 B
`mscd_init`	20 B
`tud_descriptor_configuration_cb`	8 B
`operator delete(void*, unsigned int)`	8 B
`operator new[](unsigned int)`	8 B
`tud_descriptor_device_cb`	8 B
`operator delete[](void*)`	8 B
`exit`	6 B
`SdSpiCard::errorCode() const`	4 B

Pico_Audio_SPDIF: 43 symbols moved RAM → FLASH (-5.3 KB RAM)

Symbol	Size
`amigaWifiCommand`	1.2 KB
`FatFile::rename(FatFile, char const)`	332 B
`FatPartition::init(FsBlockDeviceInterface*, unsigned char, unsigned long)`	324 B
`ExFatPartition::init(FsBlockDeviceInterface*, unsigned char, unsigned long)`	252 B
`ExFatFile::addDirCluster()`	196 B
`ExFatPartition::bitmapFind(unsigned long, unsigned long)`	192 B
`partitionTableGetVolumeStartSector(FsCache&, unsigned char)`	192 B
`ExFatPartition::bitmapModify(unsigned long, unsigned long, bool)`	164 B
`FatFile::makeUniqueSfn(FatLfn_t*)`	144 B
`ExFatFile::rename(ExFatFile, char const)`	140 B
`ExFatFile::preAllocate(unsigned long long)`	136 B
`ExFatPartition::freeClusterCount()`	136 B
`FatPartition::allocContiguous(unsigned long, unsigned long*)`	136 B
`FatPartition::freeClusterCount()`	124 B
`FatPartition::allocateCluster(unsigned long, unsigned long*)`	124 B
`FatFile::addDirCluster()`	112 B
`FatFile::fgets(char, int, char const)`	106 B
`FatFile::contiguousRange(unsigned long, unsigned long)`	106 B
`ExFatFile::fgets(char, int, char const)`	104 B
`FatPartition::fatPut(unsigned long, unsigned long)`	104 B
`FsBaseFile::copy(FsBaseFile const*)`	102 B
`ExFatPartition::fatPut(unsigned long, unsigned long)`	80 B
`ExFatPartition::freeChain(unsigned long)`	78 B
`ExFatFile::contiguousRange(unsigned long, unsigned long)`	76 B
`FatVolume::chdir(char const*)`	72 B
`FatFile::preAllocate(unsigned long)`	72 B
`ExFatVolume::chdir(char const*)`	68 B
`FatPartition::freeChain(unsigned long)`	58 B
`FatFile::getLfnChar(DirLfn_t const*, unsigned char)`	52 B
`ExFatFile::peek()`	50 B
... and 13 more

Pico_DaynaPORT: 34 symbols moved FLASH → RAM (+7.2 KB)

Symbol	Size
`mscd_xfer_cb`	1.4 KB
`ExFatFile::write(void const*, unsigned int)`	992 B
`ExFatFile::read(void*, unsigned int)`	672 B
`FatFile::write(void const*, unsigned int)`	524 B
`FatFile::readPrivate(void, unsigned int, DirFat_t*)`	498 B
`ExFatFile::seekSet(unsigned long long)`	468 B
`ExFatFile::buildSectorMap()`	444 B
`FatFile::buildSectorMap()`	358 B
`mscd_control_xfer_cb`	328 B
`FatFile::seekSet(unsigned long)`	272 B
`FatFile::readSectorsDirect(unsigned long, unsigned char*, unsigned long)`	200 B
`ExFatFile::readSectorsDirect(unsigned long, unsigned char*, unsigned long)`	200 B
`FatPartition::fatGet(unsigned long, unsigned long*)`	154 B
`tud_descriptor_string_cb`	116 B
`mscd_open`	104 B
`ExFatPartition::fatGet(unsigned long, unsigned long*)`	96 B
`FsCache::prepare(unsigned long, unsigned char)`	84 B
`ExFatPartition::dirSeek(DirPos_t*, unsigned long)`	80 B
`FsCache::sync()`	74 B
`ExFatPartition::dirCache(DirPos_t const*, unsigned char)`	68 B
`ExFatFile::dirCache(unsigned char, unsigned char)`	60 B
`FatFile::cacheDirEntry(unsigned char)`	32 B
`FatFile::readDirCache()`	32 B
`mscd_reset`	20 B
`mscd_init`	20 B
`FsBaseFile::operator=(FsBaseFile const&)`	12 B
`tud_descriptor_configuration_cb`	8 B
`operator delete(void*, unsigned int)`	8 B
`operator new[](unsigned int)`	8 B
`tud_descriptor_device_cb`	8 B
... and 4 more

Pico_DaynaPORT: 3 symbols moved RAM → FLASH (-1.2 KB RAM)

Symbol	Size
`amigaWifiCommand`	1.2 KB
`StreamFile<FsBaseFile, unsigned long long>::peek()`	34 B
`StreamFile<FatFile, unsigned long>::peek()`	10 B

Ultra: 4 symbols moved FLASH → RAM (+16 B)

Symbol	Size
`operator new(unsigned int)`	4 B
`operator delete[](void*)`	4 B
`operator new[](unsigned int)`	4 B
`operator delete(void*, unsigned int)`	4 B

Ultra: 9 symbols moved RAM → FLASH (-298 B RAM)

Symbol	Size
`tud_descriptor_device_cb`	116 B
`tud_descriptor_string_cb`	96 B
`_lseek`	16 B
`_close`	16 B
`_fstat`	16 B
`_isatty`	16 B
`tud_descriptor_configuration_cb`	12 B
`_read`	6 B
`_write`	4 B

Ultra_Wide: 4 symbols moved FLASH → RAM (+16 B)

Symbol	Size
`operator delete(void*, unsigned int)`	4 B
`operator new[](unsigned int)`	4 B
`operator delete[](void*)`	4 B
`operator new(unsigned int)`	4 B

Ultra_Wide: 9 symbols moved RAM → FLASH (-298 B RAM)

Symbol	Size
`tud_descriptor_device_cb`	116 B
`tud_descriptor_string_cb`	96 B
`_fstat`	16 B
`_lseek`	16 B
`_close`	16 B
`_isatty`	16 B
`tud_descriptor_configuration_cb`	12 B
`_read`	6 B
`_write`	4 B

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disk: fix data corruption on 256-byte sector images#362

disk: fix data corruption on 256-byte sector images#362
erichelgeson wants to merge 1 commit intomainfrom
eric/fix-256-byte

erichelgeson commented Apr 24, 2026 •

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BlueSCSI Memory Report

Memory Usage

Symbol Region Changes

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erichelgeson commented Apr 24, 2026 •

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