From b00c3317ac1d27a513a95772120bd1cb05b56cf6 Mon Sep 17 00:00:00 2001
From: Ciro Cattuto <ciro.cattuto@gmail.com>
Date: Thu, 16 Dec 2021 21:57:59 +0100
Subject: [PATCH] Implemented readBytes() and writeBytes()()

Added methods to read/write non-word-aligned byte memory blocks.
---
 README.md           |  2 ++
 examples/rtt/rtt.js | 23 ++------------
 src/dap/adi.ts      | 77 +++++++++++++++++++++++++++++++++++++++++++++
 src/dap/index.ts    | 16 ++++++++++
 4 files changed, 98 insertions(+), 20 deletions(-)

diff --git a/README.md b/README.md
index 5503736..14b9fc0 100644
--- a/README.md
+++ b/README.md
@@ -284,6 +284,8 @@ The `DAP` (Debug Access Port) layer exposes low-level access to ports, registers
 - [x] writeMem32()
 - [x] readBlock()
 - [x] writeBlock()
+- [x] readBytes()
+- [x] writeBytes()
 
 ### Processor
 
diff --git a/examples/rtt/rtt.js b/examples/rtt/rtt.js
index 2b80317..a22936c 100644
--- a/examples/rtt/rtt.js
+++ b/examples/rtt/rtt.js
@@ -109,33 +109,16 @@ class RTT {
         }).join('')
     }
 
-    async readBytes (addr, size) {
-        var sizeToRead = size;
-        let startOffset = addr % 4;
-        let endOffset = (addr + size) % 4;
-
-        if (startOffset) {
-            addr -= startOffset;
-            sizeToRead += startOffset;
-        }
-
-        if (endOffset)
-            sizeToRead += (4 - endOffset);
-
-        var data32 = await this.processor.readBlock(addr, sizeToRead / 4);
-        return new Uint8Array(data32.buffer).slice(startOffset, startOffset + size);
-    }
-
     async read (bufId) {
         var buf = this.bufUp[bufId];
 
         buf.WrOff = await this.processor.readMem32(buf.bufAddr + 12);
 
         if (buf.WrOff > buf.RdOff) {
-            var data = await this.readBytes(buf.pBuffer + buf.RdOff, buf.WrOff - buf.RdOff);
+            var data = await processor.readBytes(buf.pBuffer + buf.RdOff, buf.WrOff - buf.RdOff);
         } else if (buf.WrOff < buf.RdOff) {
-            let data1 = await this.readBytes(buf.pBuffer + buf.RdOff, buf.SizeOfBuffer - buf.RdOff);
-            let data2 = await this.readBytes(buf.pBuffer, buf.WrOff);
+            let data1 = await processor.readBytes(buf.pBuffer + buf.RdOff, buf.SizeOfBuffer - buf.RdOff);
+            let data2 = await processor.readBytes(buf.pBuffer, buf.WrOff);
             var data = new Uint8Array(data1.length + data2.length);
             data.set(data1, 0);
             data.set(data2, data1.length);
diff --git a/src/dap/adi.ts b/src/dap/adi.ts
index f5a4eb5..b72610c 100644
--- a/src/dap/adi.ts
+++ b/src/dap/adi.ts
@@ -461,4 +461,81 @@ export class ADI implements DAP {
             index += chunkSize;
         }
     }
+
+    /**
+     * Read a block of bytes from a memory access port register
+     * @param register ID of register to read from
+     * @param count The count of values to read
+     * @returns Promise of register data
+     */
+    public async readBytes(register: number, count: number): Promise<Uint8Array> {
+        // read a word-aligned chunk of 32-bit words containing the requested range, then trim it
+        let bytesToRead = count;
+        const startOffset = register & 0x03;
+        const endOffset = (register + count) & 0x03;
+
+        // include left-most 32-bit word
+        if (startOffset) {
+            register -= startOffset;
+            bytesToRead += startOffset;
+        }
+
+        // include right-most 32-bit word
+        if (endOffset) {
+            bytesToRead += (4 - endOffset);
+        }
+
+        const result = await this.readBlock(register, bytesToRead / 4);
+        return new Uint8Array(result.buffer).slice(startOffset, startOffset + count);
+    }
+
+    /**
+     * Write a block of bytes to a memory access port register
+     * @param register ID of register to write to
+     * @param values The values to write
+     * @returns Promise
+     */
+    public async writeBytes(register: number, values: Uint8Array): Promise<void> {
+        let bytesToWrite = values.length;
+        let index = 0;
+
+        // initial byte write
+        if ((bytesToWrite > 0) && (register & 0x01)) {
+            await this.writeMem8(register, values[index]);
+            bytesToWrite -= 1;
+            register += 1;
+            index += 1;
+        }
+
+        // initial 16-bit word write
+        if ((bytesToWrite > 1) && (register & 0x02)) {
+            await this.writeMem16(register, values[index] | (values[index + 1] << 8));
+            bytesToWrite -= 2;
+            register += 2;
+            index += 2;
+        }
+
+        // chunk of word-aligned 32-bit words
+        if (bytesToWrite >= 4) {
+            const chunkSize = bytesToWrite - bytesToWrite % 4;
+            const chunk = new Uint32Array(values.slice(index, index + chunkSize).buffer);
+            await this.writeBlock(register, chunk);
+            bytesToWrite -= chunkSize;
+            register += chunkSize;
+            index += chunkSize;
+        }
+
+        // trailing 16-bit word write
+        if (bytesToWrite > 1) {
+            await this.writeMem16(register, values[index] | (values[index + 1] << 8));
+            bytesToWrite -= 2;
+            register += 2;
+            index += 2;
+        }
+
+        // tailing byte write
+        if (bytesToWrite > 0) {
+            await this.writeMem8(register, values[index]);
+        }
+    }
 }
diff --git a/src/dap/index.ts b/src/dap/index.ts
index 06f7997..c5359d1 100644
--- a/src/dap/index.ts
+++ b/src/dap/index.ts
@@ -139,6 +139,22 @@ export interface DAP {
      * @returns Promise
      */
     writeBlock(register: number, values: Uint32Array): Promise<void>;
+
+    /**
+     * Read a block of bytes from a memory access port register
+     * @param register ID of register to read from
+     * @param count The count of values to read
+     * @returns Promise of register data
+     */
+    readBytes(register: number, count: number): Promise<Uint8Array>;
+
+     /**
+      * Write a block of bytes to a memory access port register
+      * @param register ID of register to write to
+      * @param values The values to write
+      * @returns Promise
+      */
+    writeBytes(register: number, values: Uint8Array): Promise<void>;
 }
 
 export * from './adi';