isolate blocks

3 files changed, 140 insertions, 0 deletions

diff --git a/src/blocks/lzssblock.nim b/src/blocks/lzssblock.nim
new file mode 100644
index 0000000..f68f665
--- /dev/null
+++ b/src/blocks/lzssblock.nim
@@ -0,0 +1,32 @@
+# 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 ../bitio/bitreader, ../bitio/bitwriter
+
+type LzssBlock* = object
+  discard
+
+proc readSerialised*(bitReader: BitReader): LzssBlock =
+  discard
+
+proc writeSerialisedTo*(lzssBlock: LzssBlock, bitWriter: BitWriter) =
+  discard
+
+proc readRaw*(bitReader: BitReader): LzssBlock =
+  discard
+
+proc writeRawTo*(lzssBlock: LzssBlock, bitWriter: BitWriter) =
+  discard
diff --git a/src/blocks/rawblock.nim b/src/blocks/rawblock.nim
new file mode 100644
index 0000000..2b32831
--- /dev/null
+++ b/src/blocks/rawblock.nim
@@ -0,0 +1,40 @@
+# 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 ../bitio/integers, ../bitio/bitreader, ../bitio/bitwriter
+
+const maxDataBitLength = high(uint16).int
+const bitLengthFieldBitLength = 2 * wordBitLength
+
+type RawBlock* = object
+  bitLength: int
+  data: seq[uint8]
+
+proc readSerialised*(bitReader: BitReader): RawBlock =
+  let bitLength = bitReader.readBits(bitLengthFieldBitLength, uint16).int
+  let data = bitReader.readSeq(bitLength, uint8)
+  RawBlock(bitLength: bitLength, data: data.data)
+
+proc writeSerialisedTo*(rawBlock: RawBlock, bitWriter: BitWriter) =
+  bitWriter.writeBits(bitLengthFieldBitLength, rawBlock.bitLength.uint16)
+  bitWriter.writeSeq(rawBlock.bitLength, rawBlock.data)
+
+proc readRaw*(bitReader: BitReader, bits: int = maxDataBitLength): RawBlock =
+  let data = bitReader.readSeq(bits, uint8)
+  RawBlock(bitLength: data.bitLength, data: data.data)
+
+proc writeRawTo*(rawBlock: RawBlock, bitWriter: BitWriter) =
+  bitWriter.writeSeq(rawBlock.bitLength, rawBlock.data)
diff --git a/src/blocks/streamblock.nim b/src/blocks/streamblock.nim
new file mode 100644
index 0000000..c904af7
--- /dev/null
+++ b/src/blocks/streamblock.nim
@@ -0,0 +1,68 @@
+# 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 sequtils
+import ../bitio/integers, ../bitio/bitreader, ../bitio/bitwriter
+import rawblock, lzssblock
+
+type BlockKind* = enum
+  uncompressed = 0b00'u8,
+  lzss = 0b01,
+  reserved1 = 0b10,
+  reserved2 = 0b11
+
+type StreamBlock* = object
+  last: bool
+  case kind: BlockKind
+    of uncompressed:
+      rawBlock: RawBlock
+    of lzss:
+      lzssBlock: LzssBlock
+    else:
+      discard
+
+proc isLast*(streamBlock: StreamBlock): bool =
+  streamBlock.last
+
+proc readSerialised*(bitReader: BitReader): StreamBlock =
+  result.last = bitReader.readBool()
+  result.kind = bitReader.readBits(2, uint8).BlockKind
+  case result.kind:
+    of uncompressed: result.rawBlock = rawblock.readSerialised(bitReader)
+    of lzss: result.lzssBlock = lzssblock.readSerialised(bitReader)
+    else: raise newException(ValueError, "unhandled block type")
+
+proc writeSerialisedTo*(streamBlock: StreamBlock, bitWriter: BitWriter) =
+  bitWriter.writeBool(streamBlock.last)
+  bitWriter.writeBits(2, streamBlock.kind.uint8)
+  case streamBlock.kind:
+    of uncompressed: streamBlock.rawBlock.writeSerialisedTo(bitWriter)
+    of lzss: streamBlock.lzssBlock.writeSerialisedTo(bitWriter)
+    else: raise newException(ValueError, "unhandled block type")
+
+proc readRaw*(bitReader: BitReader, kind: BlockKind = uncompressed): StreamBlock =
+  result.kind = kind
+  case kind:
+    of uncompressed: result.rawBlock = rawblock.readRaw(bitReader)
+    of lzss: result.lzssBlock = lzssblock.readRaw(bitReader)
+    else: raise newException(ValueError, "unhandled block type")
+  result.last = bitReader.atEnd()
+
+proc writeRawTo*(streamBlock: StreamBlock, bitWriter: BitWriter) =
+  case streamBlock.kind:
+    of uncompressed: streamBlock.rawBlock.writeRawTo(bitWriter)
+    of lzss: streamBlock.lzssBlock.writeRawTo(bitWriter)
+    else: raise newException(ValueError, "unhandled block type")