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Add minimal sparse handler and split images up based on sparse chunks when flashing if the image is too big #4

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dbdcaa4
Add minimal sparse handler
halal-beef Dec 13, 2025
cbd3359
Add sparse splitting support to flashing command
halal-beef Dec 13, 2025
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186 changes: 186 additions & 0 deletions FastBootCommands.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -21,9 +21,12 @@
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography.Xml;
using static FastBoot.Sparse;

namespace FastBoot
{
Expand Down Expand Up @@ -264,6 +267,189 @@ public static bool RebootBootloader(this FastBootTransport fastBootTransport)
public static bool FlashPartition(this FastBootTransport fastBootTransport, string partition, Stream stream)
{
FastBootStatus status;
uint maxDownloadSize = 0;
string deviceResponse;

if(!GetVariable(fastBootTransport, "max-download-size", out deviceResponse)) return false;
maxDownloadSize = Convert.ToUInt32(deviceResponse);

if (stream.Length > maxDownloadSize)
{
byte[] image_magic = new byte[4];

try
{
stream.Read(image_magic, 0, 4);
if(BitConverter.ToUInt32(image_magic) == Sparse.sparse_magic)
{
byte[] sparseFileHeaderBuffer = new byte[28];
byte[] sparseChunkHeaderBuffer = new byte[12];
sparseFileHeader fileHeader;

List<byte[]> chunks = new();
uint blockPosition = 0;
int availableSpace;

stream.Position = 0;

stream.ReadExactly(sparseFileHeaderBuffer, 0, 28);
fileHeader = ReadSparseFileHeader(sparseFileHeaderBuffer);
availableSpace = (int)maxDownloadSize - (int)fileHeader.fileHeaderSize;

for (int i = 0; i < fileHeader.totalChunks; i++)
{
stream.ReadExactly(sparseChunkHeaderBuffer, 0, 12);
sparseChunkHeader chunkHeader = ReadSparseChunkHeader(sparseChunkHeaderBuffer);

if (chunkHeader.totalSize > availableSpace && chunks.Count > 0)
{
sparseFileHeader newFileHeader = fileHeader;
int offset = fileHeader.fileHeaderSize;

uint padding_blocks = fileHeader.totalBlocks - blockPosition;
if (padding_blocks > 0)
{
sparseChunkHeader dummyChunk = new sparseChunkHeader
{
chunkType = (ushort)chunkTypes.DONT_CARE,
reserved = 0,
chunkSize = padding_blocks,
totalSize = fileHeader.chunkHeaderSize
};
chunks.Add(ChunkHeaderToBytes(dummyChunk));
}

newFileHeader.totalChunks = (uint)chunks.Count;

byte[] fileBuffer = new byte[HeaderToBytes(newFileHeader).Length + chunks.Sum(chunk => chunk.Length)];
Buffer.BlockCopy(HeaderToBytes(newFileHeader), 0, fileBuffer, 0, 28);

foreach (byte[] chunk in chunks)
{
Buffer.BlockCopy(chunk, 0, fileBuffer, offset, chunk.Length);
offset += chunk.Length;
}

using (MemoryStream ms = new MemoryStream(fileBuffer))
{
try
{
(status, string _, byte[] _) = fastBootTransport.SendData(ms);
}
catch
{
return false;
}

if (status != FastBootStatus.OKAY)
{
return false;
}

try
{
(FastBootStatus status, string response, byte[] rawResponse)[] responses = fastBootTransport.SendCommand($"flash:{partition}");
(status, string _, byte[] _) = responses.Last();
}
catch
{
return false;
}

if (status != FastBootStatus.OKAY)
{
return false;
}
}

chunks.Clear();
availableSpace = (int)maxDownloadSize - (int)fileHeader.fileHeaderSize;

if (blockPosition > 0)
{
sparseChunkHeader dummyChunk = new sparseChunkHeader
{
chunkType = (ushort)chunkTypes.DONT_CARE,
reserved = 0,
chunkSize = blockPosition,
totalSize = fileHeader.chunkHeaderSize
};
chunks.Add(ChunkHeaderToBytes(dummyChunk));
availableSpace -= fileHeader.chunkHeaderSize;
}
}

byte[] chunk_data = new byte[chunkHeader.totalSize];
Buffer.BlockCopy(sparseChunkHeaderBuffer, 0, chunk_data, 0, 12);

int payload = (int)chunkHeader.totalSize - 12;
stream.ReadExactly(chunk_data, 12, payload);

chunks.Add(chunk_data);
blockPosition += chunkHeader.chunkSize;
availableSpace -= (int)chunkHeader.totalSize;
}

if (chunks.Count > 0)
{
sparseFileHeader newFileHeader = fileHeader;
int offset = fileHeader.fileHeaderSize;

newFileHeader.totalChunks = (uint)chunks.Count;

byte[] fileBuffer = new byte[HeaderToBytes(newFileHeader).Length + chunks.Sum(chunk => chunk.Length)];
Buffer.BlockCopy(HeaderToBytes(newFileHeader), 0, fileBuffer, 0, 28);

foreach (byte[] chunk in chunks)
{
Buffer.BlockCopy(chunk, 0, fileBuffer, offset, chunk.Length);
offset += chunk.Length;
}

using (MemoryStream ms = new MemoryStream(fileBuffer))
{
try
{
(status, string _, byte[] _) = fastBootTransport.SendData(ms);
}
catch
{
return false;
}

if (status != FastBootStatus.OKAY)
{
return false;
}

try
{
(FastBootStatus status, string response, byte[] rawResponse)[] responses = fastBootTransport.SendCommand($"flash:{partition}");
(status, string _, byte[] _) = responses.Last();
}
catch
{
return false;
}

if (status != FastBootStatus.OKAY)
{
return false;
}
}
}
return true;
}
else
{
return false; // TODO: Handle non-sparse but large images (most likely just converting them into raw chunks and sending them off).
}
}
catch
{
return false;
}
}

try
{
Expand Down
121 changes: 121 additions & 0 deletions Sparse.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,121 @@
using System;
using System.IO;

namespace FastBoot
{
internal class Sparse
{
public static readonly uint sparse_magic = 0xED26FF3A;

public enum chunkTypes
{
RAW = 0xCAC1,
FILL,
DONT_CARE,
CRC32
}

public struct sparseFileHeader
{
public uint magic;
public ushort majorVersion;
public ushort minorVersion;
public ushort fileHeaderSize;
public ushort chunkHeaderSize;
public uint blockSize;
public uint totalBlocks;
public uint totalChunks;
public uint imageChecksum;
}

public struct sparseChunkHeader
{
public ushort chunkType;
public ushort reserved;
public uint chunkSize;
public uint totalSize;
}

private static void VerifySparseFileHeader(sparseFileHeader fileHeader)
{
if (fileHeader.magic != sparse_magic) throw new Exception("Invalid sparse magic");
if (fileHeader.majorVersion > 1) throw new Exception("Sparse format too new");
if (fileHeader.fileHeaderSize != 28 && fileHeader.majorVersion == 1) throw new Exception("Invalid file header size");
if (fileHeader.chunkHeaderSize != 12 && fileHeader.majorVersion == 1) throw new Exception("Invalid chunk header size");
if (fileHeader.blockSize % 4 != 0) throw new Exception("Invalid block size");
}

public static sparseFileHeader ReadSparseFileHeader(byte[] buffer)
{
sparseFileHeader fileHeader = new();

using (var ms = new MemoryStream(buffer))
using (var br = new BinaryReader(ms))
{
fileHeader.magic = br.ReadUInt32();
fileHeader.majorVersion = br.ReadUInt16();
fileHeader.minorVersion = br.ReadUInt16();
fileHeader.fileHeaderSize = br.ReadUInt16();
fileHeader.chunkHeaderSize = br.ReadUInt16();
fileHeader.blockSize = br.ReadUInt32();
fileHeader.totalBlocks = br.ReadUInt32();
fileHeader.totalChunks = br.ReadUInt32();
fileHeader.imageChecksum = br.ReadUInt32();
}

VerifySparseFileHeader(fileHeader);

return fileHeader;
}

public static sparseChunkHeader ReadSparseChunkHeader(byte[] buffer)
{
sparseChunkHeader chunk_header = new();

using (var ms = new MemoryStream(buffer))
using (var br = new BinaryReader(ms))
{
chunk_header.chunkType = br.ReadUInt16();
chunk_header.reserved = br.ReadUInt16();
chunk_header.chunkSize = br.ReadUInt32();
chunk_header.totalSize = br.ReadUInt32();
}
return chunk_header;
}

public static byte[] HeaderToBytes(sparseFileHeader fileHeader)
{
using (var ms = new MemoryStream())
using (var bw = new BinaryWriter(ms))
{
bw.Write(fileHeader.magic);
bw.Write(fileHeader.majorVersion);
bw.Write(fileHeader.minorVersion);
bw.Write(fileHeader.fileHeaderSize);
bw.Write(fileHeader.chunkHeaderSize);
bw.Write(fileHeader.blockSize);
bw.Write(fileHeader.totalBlocks);
bw.Write(fileHeader.totalChunks);
bw.Write(fileHeader.imageChecksum);

return ms.ToArray();
}
}

public static byte[] ChunkHeaderToBytes(sparseChunkHeader chunk)
{
if (chunk.chunkType != (uint)chunkTypes.DONT_CARE) throw new Exception("Only DONT_CARE chunks can be generated in this lib.");

using (var ms = new MemoryStream())
using (var bw = new BinaryWriter(ms))
{
bw.Write(chunk.chunkType);
bw.Write(chunk.reserved);
bw.Write(chunk.chunkSize);
bw.Write(chunk.totalSize);

return ms.ToArray();
}
}
}
}