From 33eadb554917fb1a459dbc3768b7a93102cd307b Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Tue, 11 Jul 2017 22:41:10 -0400
Subject: [PATCH] Started taking further steps towards CSW support; reading the
 ZLib documentation is next.

---
 Storage/Tape/Formats/CSW.cpp | 60 ++++++++++++++++++++++++++++++++++++
 Storage/Tape/Formats/CSW.hpp | 11 +++++++
 Storage/Tape/Tape.hpp        |  2 ++
 3 files changed, 73 insertions(+)

diff --git a/Storage/Tape/Formats/CSW.cpp b/Storage/Tape/Formats/CSW.cpp
index 957c8a448..9ce4b090f 100644
--- a/Storage/Tape/Formats/CSW.cpp
+++ b/Storage/Tape/Formats/CSW.cpp
@@ -12,8 +12,68 @@ using namespace Storage::Tape;
 
 CSW::CSW(const char *file_name) :
 	Storage::FileHolder(file_name) {
+	if(file_stats_.st_size < 0x20) throw ErrorNotCSW;
+
+	// Check signature.
+	char identifier[22];
+	char signature[] = "Compressed Square Wave";
+	fread(identifier, 1, 22, file_);
+	if(memcmp(identifier, signature, strlen(signature))) throw ErrorNotCSW;
+
+	// Check terminating byte.
+	if(fgetc(file_) != 0x1a) throw ErrorNotCSW;
+
+	// Get version file number.
+	uint8_t major_version = (uint8_t)fgetc(file_);
+	uint8_t minor_version = (uint8_t)fgetc(file_);
+
+	// Reject if this is an unknown version.
+	if(major_version > 2 || !major_version || minor_version > 1) throw ErrorNotCSW;
+
+	// The header now diverges based on version.
+	if(major_version == 1) {
+		pulse_.length.clock_rate = fgetc16le();
+
+		if(fgetc(file_) != 1) throw ErrorNotCSW;
+		compression_type_ = RLE;
+
+		pulse_.type = (fgetc(file_) & 1) ? Pulse::High : Pulse::Low;
+
+		fseek(file_, 0x20, SEEK_SET);
+	} else {
+		pulse_.length.clock_rate = fgetc32le();
+		number_of_waves_ = fgetc32le();
+		switch(fgetc(file_)) {
+			case 1: compression_type_ = RLE;	break;
+			case 2: compression_type_ = ZRLE;	break;
+			default: throw ErrorNotCSW;
+		}
+
+		pulse_.type = (fgetc(file_) & 1) ? Pulse::High : Pulse::Low;
+		uint8_t extension_length = (uint8_t)fgetc(file_);
+
+		if(file_stats_.st_size < 0x34 + extension_length) throw ErrorNotCSW;
+		fseek(file_, 0x34 + extension_length, SEEK_SET);
+	}
+
+	if(compression_type_ == ZRLE) {
+		inflation_stream_.zalloc = Z_NULL;
+		inflation_stream_.zfree = Z_NULL;
+		inflation_stream_.opaque = Z_NULL;
+		inflation_stream_.avail_in = 0;
+		inflation_stream_.next_in = Z_NULL;
+		int result = inflateInit(&inflation_stream_);
+		if(result != Z_OK) throw ErrorNotCSW;
+	}
 }
 
+CSW::~CSW() {
+	if(compression_type_ == ZRLE) {
+		inflateEnd(&inflation_stream_);
+	}
+}
+
+
 bool CSW::is_at_end() {
 	return true;
 }
diff --git a/Storage/Tape/Formats/CSW.hpp b/Storage/Tape/Formats/CSW.hpp
index ed98b3bed..4063e530b 100644
--- a/Storage/Tape/Formats/CSW.hpp
+++ b/Storage/Tape/Formats/CSW.hpp
@@ -12,6 +12,8 @@
 #include "../Tape.hpp"
 #include "../../FileHolder.hpp"
 
+#include <zlib.h>
+
 namespace Storage {
 namespace Tape {
 
@@ -26,6 +28,7 @@ class CSW: public Tape, public Storage::FileHolder {
 			@throws ErrorNotCSW if this file could not be opened and recognised as a valid CSW file.
 		*/
 		CSW(const char *file_name);
+		~CSW();
 
 		enum {
 			ErrorNotCSW
@@ -37,6 +40,14 @@ class CSW: public Tape, public Storage::FileHolder {
 	private:
 		void virtual_reset();
 		Pulse virtual_get_next_pulse();
+
+		Pulse pulse_;
+		enum CompressionType {
+			RLE,
+			ZRLE
+		} compression_type_;
+		uint32_t number_of_waves_;
+		z_stream inflation_stream_;
 };
 
 }
diff --git a/Storage/Tape/Tape.hpp b/Storage/Tape/Tape.hpp
index 7ed5920da..483f8e551 100644
--- a/Storage/Tape/Tape.hpp
+++ b/Storage/Tape/Tape.hpp
@@ -58,6 +58,8 @@ class Tape {
 		/// Advances or reverses the tape to the last time before or at @c time from which a pulse starts.
 		virtual void seek(Time &time);
 
+		virtual ~Tape() {};
+
 	private:
 		Time current_time_, next_time_;