Implement rawblock

2 files changed, 97 insertions, 0 deletions

diff --git a/src/rawblock.nim b/src/rawblock.nim
new file mode 100644
index 0000000..bdbfc71
--- /dev/null
+++ b/src/rawblock.nim
@@ -0,0 +1,40 @@
+# "à-la-gzip" gzip-like LZSS compressor
+# Copyright (C) 2018  Pacien TRAN-GIRARD
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+import integers, bitstream
+
+const maxDataBitLength = 100_000_000 * wordBitLength # 100MB
+const bitLengthFieldBitLength = 2 * wordBitLength
+
+type RawBlock* = object
+  bitLength: int
+  data: seq[uint8]
+
+proc readSerialised*(bitStream: BitStream): RawBlock =
+  let bitLength = bitStream.readBits(bitLengthFieldBitLength, uint16).int
+  let data = readSeq(bitStream, bitLength, uint8)
+  RawBlock(bitLength: bitLength, data: data.data)
+
+proc writeSerialisedTo*(rawBlock: RawBlock, bitStream: BitStream) =
+  bitStream.writeBits(bitLengthFieldBitLength, rawBlock.bitLength.uint16)
+  writeSeq(bitStream, rawBlock.bitLength, rawBlock.data)
+
+proc readRaw*(bitStream: BitStream, bits: int = maxDataBitLength): RawBlock =
+  let data = readSeq(bitStream, bits, uint8)
+  RawBlock(bitLength: data.bitLength, data: data.data)
+
+proc writeRawTo*(rawBlock: RawBlock, bitStream: BitStream) =
+  writeSeq(bitStream, rawBlock.bitLength, rawBlock.data)
diff --git a/tests/trawblock.nim b/tests/trawblock.nim
new file mode 100644
index 0000000..1e92c60
--- /dev/null
+++ b/tests/trawblock.nim
@@ -0,0 +1,57 @@
+# "à-la-gzip" gzip-like LZSS compressor
+# Copyright (C) 2018  Pacien TRAN-GIRARD
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+import unittest, streams
+import bitstream, rawblock
+
+suite "rawblock":
+  test "serialise":
+    let rawStream = newStringStream()
+    defer: rawStream.close()
+    rawStream.write(0xFEDC_BA98_7654_3210'u64)
+    rawStream.setPosition(0)
+    let rawBitStream = rawStream.bitStream()
+    let rawBlock = rawblock.readRaw(rawBitStream)
+
+    let outputStream = newStringStream()
+    defer: outputStream.close()
+    let outputBitStream = outputStream.bitStream()
+    rawBlock.writeSerialisedTo(outputBitStream)
+    outputBitStream.flush()
+
+    outputStream.setPosition(0)
+    check outputStream.readUint16() == 64
+    check outputStream.readUint64() == 0xFEDC_BA98_7654_3210'u64
+    check outputStream.atEnd()
+
+  test "deserialise":
+    let serialisedStream = newStringStream()
+    defer: serialisedStream.close()
+    serialisedStream.write(60'u16)
+    serialisedStream.write(0xFEDC_BA98_7654_3210'u64)
+    serialisedStream.setPosition(0)
+    let serialisedBitStream = serialisedStream.bitStream()
+    let rawBlock = rawBlock.readSerialised(serialisedBitStream)
+
+    let outputStream = newStringStream()
+    defer: outputStream.close()
+    let outputBitStream = outputStream.bitStream()
+    rawBlock.writeRawTo(outputBitStream)
+    outputBitStream.flush()
+
+    outputStream.setPosition(0)
+    check outputStream.readUint64 == 0x0EDC_BA98_7654_3210'u64
+    check outputStream.atEnd()