Writer example

README.md

@@ -97,7 +97,45 @@ The library is meant to be embedded directly into another project.
 
 ## Writing example
 
-    TBA
+    #include"eebie/writer.h"
+
+    #include<stdio.h>
+    #include<stdlib.h>
+
+    static void *on_alloc(EBMLWriter *w, void *p, size_t sz) {
+        return realloc(p, sz);
+    }
+
+    static size_t on_write(EBMLWriter *w, const void *p, size_t sz) {
+        FILE *fp = w->ud;
+        
+        return fwrite(p, 1, sz, fp);
+    }
+
+    int main() {
+        EBMLWriter w;
+        ebml_writer_init(&w);
+        
+        FILE *output = fopen("test.ebml", "wb");
+        w.ud = output;
+        
+        w.eventWrite = on_write;
+        w.eventAlloc = on_alloc;
+        
+        ebml_writer_push(&w, 0x1A45DFA3);
+            ebml_writer_put(&w, 0x4286, EBML_UNSIGNED_INTEGER, (EBMLPrimitive) {.uInt = 1});
+            ebml_writer_put(&w, 0x4282, EBML_STRING, (EBMLPrimitive) {.string = "excrement"});
+        ebml_writer_pop(&w);
+        
+        // Unknown-sized element must not have corresponding pop
+        ebml_writer_push_ind(&w, 0x18538067);
+        
+        ebml_writer_put(&w, 0x4123, EBML_STRING, (EBMLPrimitive) {.string = "yodel"});
+        
+        while(!ebml_writer_flush(&w));
+        
+        fclose(output);
+    }
 
 ## `schemagen`
 

eebie/ebml.h

@@ -2,6 +2,7 @@
 #define EEBIE_H
 
 #include<stdint.h>
+#include<stddef.h>
 
 typedef enum EBMLElementType {
 	EBML_SIGNED_INTEGER,
@@ -15,13 +16,18 @@ typedef enum EBMLElementType {
 	EBML_BINARY,
 } EBMLElementType;
 
+typedef struct EBMLBinary {
+	uint8_t *ptr;
+	size_t length;
+} EBMLBinary;
+
 typedef union EBMLPrimitive {
 	int64_t sInt;
 	uint64_t uInt;
 	float flt4;
 	double flt8;
 	const char *string;
-	const uint8_t *binary;
+	const EBMLBinary binary;
 	uint64_t date;
 } EBMLPrimitive;
 

eebie/writer.c

@@ -2,7 +2,8 @@
 
 #include<string.h>
 #include<endian.h>
-#include<stdlib.h>
+#include<stddef.h>
+#include<assert.h>
 
 static uint64_t VARINT_MASKS[] = {0, 0x80L, 0xC000L, 0xE00000L, 0xF0000000L, 0xF800000000L, 0xFC0000000000L, 0xFE000000000000L, 0L};
 
@@ -41,7 +42,7 @@ static void advance(EBMLWriter *this, uint64_t amount) {
 
 static void add(EBMLWriter *this, const void *data, size_t length) {
 	if(this->bufferLen + length > this->bufferCapacity) {
-		this->buffer = realloc(this->buffer, (this->bufferLen + length + 1023) & ~1023);
+		this->buffer = this->eventAlloc(this, this->buffer, (this->bufferLen + length + 1023) & ~1023);
 	}
 	
 	memcpy(this->buffer + this->bufferLen, data, length);
@@ -61,8 +62,18 @@ static void add_varint(EBMLWriter *this, uint64_t i) {
 
 void ebml_writer_init(EBMLWriter *this) {
 	memset(this, 0, sizeof(EBMLWriter));
+}
 
-	this->buffer = calloc(this->bufferCapacity = 1024, 1);
+void ebml_writer_free(EBMLWriter *this) {
+	this->eventAlloc(this, this->buffer, 0);
+}
+
+void ebml_writer_push_ind(EBMLWriter *this, uint64_t id) {
+	add_varint(this, id);
+	
+	add(this, &(uint64_t) {htobe64(0x01FFFFFFFFFFFFFFL)}, sizeof(uint64_t)); // UNKNOWN-SIZED ELEMENT
+	
+	while(!ebml_writer_flush(this));
 }
 
 void ebml_writer_push(EBMLWriter *this, uint64_t id) {
@@ -74,6 +85,24 @@ void ebml_writer_push(EBMLWriter *this, uint64_t id) {
 }
 
 void ebml_writer_pop(EBMLWriter *this) {
+	this->currentDepth--;
+	
+	uint64_t newSize = this->stack[this->currentDepth];
+	uint64_t *s = (uint64_t*) &this->buffer[this->bufferLen - newSize - 8];
+	*s = htobe64(0x0100000000000000L | newSize);
+	
+	if(this->currentDepth == 0) {
+		while(!ebml_writer_flush(this));
+	}
+}
+
+bool ebml_writer_flush(EBMLWriter *this) {
+	size_t written = this->eventWrite(this, this->buffer, this->bufferLen);
+	
+	memmove(this->buffer, this->buffer + written, this->bufferLen - written);
+	this->bufferLen -= written;
+	
+	return this->bufferLen == 0;
 }
 
 void ebml_writer_put(EBMLWriter *this, uint64_t id, EBMLElementType type, EBMLPrimitive primitive) {
@@ -89,9 +118,11 @@ void ebml_writer_put(EBMLWriter *this, uint64_t id, EBMLElementType type, EBMLPr
 		len = 8;
 	} else if(type == EBML_STRING) {
 		len = strlen(primitive.string);
+	} else if(type == EBML_BINARY) {
+		len = primitive.binary.length;
 	} else if(type == EBML_DATE) {
 		len = 8;
-	} else abort();
+	} else assert(0);
 	
 	add_varint(this, encode_int(len));
 	
@@ -100,13 +131,17 @@ void ebml_writer_put(EBMLWriter *this, uint64_t id, EBMLElementType type, EBMLPr
 		add(this, (uint8_t*) &primitive.uInt + 8 - len, len);
 	} else if(type == EBML_FLOAT4) {
 		uint32_t fl = *(uint32_t*) &primitive.flt4;
+		fl = htobe32(fl);
 		add(this, &fl, 4);
 	} else if(type == EBML_FLOAT8) {
 		uint64_t fl = *(uint64_t*) &primitive.flt8;
+		fl = htobe64(fl);
 		add(this, &fl, 8);
 	} else if(type == EBML_STRING) {
 		add(this, primitive.string, len);
+	} else if(type == EBML_BINARY) {
+		add(this, primitive.binary.ptr, primitive.binary.length);
 	} else if(type == EBML_DATE) {
 		add(this, &primitive.date, 8);
-	} else abort();
+	} else assert(0);
 }

eebie/writer.h

@@ -4,16 +4,21 @@
 #include"ebml.h"
 
 #include<stddef.h>
+#include<stdbool.h>
 
 #define EBML_WRITE_MAXIMUM_DEPTH 128
 
-typedef size_t(*EBMLWriteCallback)(void *ud, const void *data, size_t length);
+struct EBMLWriter;
 
-typedef struct {
+typedef size_t(*EBMLEventWrite)(struct EBMLWriter*, const void *data, size_t length);
+typedef void*(*EBMLEventAlloc)(struct EBMLWriter*, void *data, size_t length);
+
+typedef struct EBMLWriter {
 	int currentDepth;
 	uint64_t stack[EBML_WRITE_MAXIMUM_DEPTH];
 	
-	EBMLWriteCallback callbackWrite;
+	EBMLEventWrite eventWrite;
+	EBMLEventAlloc eventAlloc;
 	
 	uint8_t *buffer;
 	size_t bufferLen;
@@ -23,10 +28,14 @@ typedef struct {
 } EBMLWriter;
 
 void ebml_writer_init(EBMLWriter *this);
+void ebml_writer_free(EBMLWriter *this);
 
+void ebml_writer_push_ind(EBMLWriter *this, uint64_t id);
 void ebml_writer_push(EBMLWriter *this, uint64_t id);
 void ebml_writer_pop(EBMLWriter *this);
 
+bool ebml_writer_flush(EBMLWriter *this);
+
 void ebml_writer_put(EBMLWriter *this, uint64_t id, EBMLElementType type, EBMLPrimitive primitive);
 
 #endif