Merge 7c8d829 into 11677db

src/Partition/ReadablePartition.js

@@ -6,9 +6,10 @@ const { assert } = require('../util');
 const DEFAULT_READ_BUFFER_SIZE = 64 * 1024;
 const DOCUMENT_HEADER_SIZE = 16;
 const DOCUMENT_ALIGNMENT = 4;
+const DOCUMENT_SEPARATOR = "\x00\x00\x1E\n";
 
-// node-event-store partition V02
-const HEADER_MAGIC = "nesprt02";
+// node-event-store partition V03
+const HEADER_MAGIC = "nesprt03";
 
 class CorruptFileError extends Error {}
 class InvalidDataSizeError extends Error {}
@@ -160,8 +161,8 @@ class ReadablePartition extends events.EventEmitter {
      * @returns {number} The size of the data including header, padded to 16 bytes alignment and ended with a line break.
      */
     documentWriteSize(dataSize) {
-        const padSize = (DOCUMENT_ALIGNMENT - ((dataSize + 1) % DOCUMENT_ALIGNMENT)) % DOCUMENT_ALIGNMENT;
-        return dataSize + 1 + padSize + DOCUMENT_HEADER_SIZE;
+        const padSize = (DOCUMENT_ALIGNMENT - ((dataSize + 4 + DOCUMENT_SEPARATOR.length) % DOCUMENT_ALIGNMENT)) % DOCUMENT_ALIGNMENT;
+        return dataSize + DOCUMENT_SEPARATOR.length + 4 + padSize + DOCUMENT_HEADER_SIZE;
     }
 
     /**
@@ -221,7 +222,8 @@ class ReadablePartition extends events.EventEmitter {
             throw new InvalidDataSizeError(`Invalid document size ${dataSize} at position ${position}, expected ${size}.`);
         }
 
-        if (position + dataSize + DOCUMENT_HEADER_SIZE > this.size) {
+        const writeSize = this.documentWriteSize(dataSize);
+        if (position + writeSize > this.size) {
             throw new CorruptFileError(`Invalid document at position ${position}. This may be caused by an unfinished write.`);
         }
 
@@ -249,6 +251,25 @@ class ReadablePartition extends events.EventEmitter {
         return ({ buffer: this.readBuffer, cursor: bufferCursor, length: this.readBufferLength });
     }
 
+    /**
+     * Prepare the read buffer for reading *before* the specified position. Don't try to reader *after* the returned cursor.
+     *
+     * @protected
+     * @param {number} position The position in the file to prepare the read buffer for reading before.
+     * @returns {{ buffer: Buffer|null, cursor: number, length: number }} A reader object with properties `buffer`, `cursor` and `length`.
+     */
+    prepareReadBufferBackwards(position) {
+        if (position < 0) {
+            return ({ buffer: null, cursor: 0, length: 0 });
+        }
+        let bufferCursor = position - this.readBufferPos;
+        if (this.readBufferPos < 0 || (this.readBufferPos > 0 && bufferCursor < DOCUMENT_SEPARATOR.length + 4)) {
+            this.fillBuffer(Math.max(position - this.readBuffer.byteLength, 0));
+            bufferCursor = this.readBufferLength;
+        }
+        return ({ buffer: this.readBuffer, cursor: bufferCursor, length: this.readBufferLength });
+    }
+
     /**
      * Read the data from the given position.
      *
@@ -290,6 +311,45 @@ class ReadablePartition extends events.EventEmitter {
         return reader.buffer.toString('utf8', dataPosition, dataPosition + dataSize);
     }
 
+    /**
+     * Find the start position of the document that precedes the given position.
+     *
+     * @protected
+     * @param {number} position The file position to read backwards from.
+     * @returns {number|boolean} The start position of the first document before the given position or false if no header could be found.
+     */
+    findDocumentPositionBefore(position) {
+        assert(this.fd, 'Partition is not opened.');
+        if (position <= 0) {
+            return false;
+        }
+
+        assert((position % DOCUMENT_ALIGNMENT) === 0, `Invalid read position. Needs to be a multiple of ${DOCUMENT_ALIGNMENT}.`);
+
+        const separatorSize = DOCUMENT_SEPARATOR.length;
+        // Optimization if we are at an exact document boundary, where we can just read the document size
+        let reader = this.prepareReadBufferBackwards(position);
+        const block = reader.buffer.toString('ascii', reader.cursor - separatorSize, reader.cursor);
+        if (block === DOCUMENT_SEPARATOR) {
+            const dataSize = reader.buffer.readUInt32BE(reader.cursor - separatorSize - 4);
+            return position - this.documentWriteSize(dataSize);
+        }
+
+        do {
+            reader = this.prepareReadBufferBackwards(position - separatorSize);
+
+            const bufferSeparatorPosition = reader.buffer.lastIndexOf(DOCUMENT_SEPARATOR, reader.cursor - separatorSize, 'ascii');
+            if (bufferSeparatorPosition >= 0) {
+                position = this.readBufferPos + bufferSeparatorPosition + separatorSize;
+                break;
+            }
+            position -= this.readBufferLength;
+        } while (position > 0);
+        return position;
+        /*const header = this.readDocumentHeader(reader.buffer, reader.cursor, position);
+        return ({ position, ...header });*/
+    }
+
     /**
      * @api
      * @returns {Generator<string>} A generator that returns all documents in this partition.
@@ -303,6 +363,20 @@ class ReadablePartition extends events.EventEmitter {
         }
     }
 
+    /**
+     * @api
+     * @returns {Generator<string>} A generator that returns all documents in this partition in reverse order.
+     */
+    *readAllBackwards() {
+        let position = this.size;
+        while ((position = this.findDocumentPositionBefore(position)) !== false) {
+            const data = this.readFrom(position);
+            if (data === false) {
+                break;
+            }
+            yield data;
+        }
+    }
 }
 
 module.exports = ReadablePartition;

src/Partition/WritablePartition.js

@@ -7,17 +7,18 @@ const Clock = require('../Clock');
 const DEFAULT_WRITE_BUFFER_SIZE = 16 * 1024;
 const DOCUMENT_HEADER_SIZE = 16;
 const DOCUMENT_ALIGNMENT = 4;
-const DOCUMENT_PAD = ' '.repeat(15) + "\n";
+const DOCUMENT_SEPARATOR = "\x00\x00\x1E\n";
+const DOCUMENT_PAD = ' '.repeat(16 - 4 - DOCUMENT_SEPARATOR.length)/* + DOCUMENT_SEPARATOR*/;
 
 const NES_EPOCH = new Date('2020-01-01T00:00:00');
 
 /**
  * @param {number} dataSize
- * @returns {string} The data padded to 16 bytes alignment and ended with a line break.
+ * @returns {string} The data padded to 16 bytes alignment and ended with \0x1E (record separator) and a line break.
  */
 function padData(dataSize) {
-    const padSize = (DOCUMENT_ALIGNMENT - ((dataSize + 1) % DOCUMENT_ALIGNMENT)) % DOCUMENT_ALIGNMENT;
-    return DOCUMENT_PAD.substr(-padSize - 1);
+    const padSize = (DOCUMENT_ALIGNMENT - ((dataSize + 4 + DOCUMENT_SEPARATOR.length) % DOCUMENT_ALIGNMENT)) % DOCUMENT_ALIGNMENT;
+    return DOCUMENT_PAD.substr(0, padSize);
 }
 
 /**
@@ -218,6 +219,11 @@ class WritablePartition extends ReadablePartition {
         let bytesWritten = 0;
         bytesWritten += fs.writeSync(this.fd, dataHeader);
         bytesWritten += fs.writeSync(this.fd, data);
+        bytesWritten += fs.writeSync(this.fd, padData(dataSize));
+        const dataSizeBuffer = Buffer.alloc(4);
+        dataSizeBuffer.writeUInt32BE(dataSize, 0);
+        bytesWritten += fs.writeSync(this.fd, dataSizeBuffer);
+        bytesWritten += fs.writeSync(this.fd, DOCUMENT_SEPARATOR);
         if (typeof callback === 'function') {
             process.nextTick(callback);
         }
@@ -240,6 +246,10 @@ class WritablePartition extends ReadablePartition {
         let bytesWritten = 0;
         bytesWritten += this.writeDocumentHeader(this.writeBuffer, this.writeBufferCursor, dataSize, sequenceNumber);
         bytesWritten += this.writeBuffer.write(data, this.writeBufferCursor + bytesWritten, 'utf8');
+        bytesWritten += this.writeBuffer.write(padData(dataSize), this.writeBufferCursor + bytesWritten, 'utf8');
+        this.writeBuffer.writeUInt32BE(dataSize, this.writeBufferCursor + bytesWritten);
+        bytesWritten += 4;
+        bytesWritten += this.writeBuffer.write(DOCUMENT_SEPARATOR, this.writeBufferCursor + bytesWritten, 'utf8');
         this.writeBufferCursor += bytesWritten;
         this.writeBufferDocuments++;
         if (typeof callback === 'function') {
@@ -267,7 +277,6 @@ class WritablePartition extends ReadablePartition {
         const dataSize = Buffer.byteLength(data, 'utf8');
         assert(dataSize <= 64 * 1024 * 1024, 'Document is too large! Maximum is 64 MB');
 
-        data += padData(dataSize);
         const dataPosition = this.size;
         if (dataSize + DOCUMENT_HEADER_SIZE >= this.writeBuffer.byteLength * 4 / 5) {
             this.size += this.writeUnbuffered(data, dataSize, sequenceNumber, callback);

test/Partition.spec.js

@@ -156,6 +156,36 @@ describe('Partition', function() {
 
     });
 
+    describe('readAll', function() {
+
+        it('reads all documents in write order', function() {
+            partition.open();
+            fillPartition(50, i => 'foo-' + i.toString());
+            partition.close();
+            partition.open();
+            let i = 1;
+            for (let data of partition.readAll()) {
+                expect(data).to.be('foo-' + i.toString());
+                i++;
+            }
+            expect(i).to.be(51);
+        });
+
+        it('reads all documents in backwards write order', function() {
+            partition.open();
+            fillPartition(50, i => 'foo-' + i.toString());
+            partition.close();
+            partition.open();
+            let i = 50;
+            for (let data of partition.readAllBackwards()) {
+                expect(data).to.be('foo-' + i.toString());
+                i--;
+            }
+            expect(i).to.be(0);
+        });
+
+    });
+
     describe('readFrom', function() {
 
         it('returns false when partition is not open', function() {