Add support for mmap(2)

libs/core/mmap.cpp

@@ -0,0 +1,76 @@
+#include "pxt.h"
+
+#include <unistd.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+namespace pxt {
+PXT_VTABLE_CTOR(MMap) {
+    length = 0;
+    fd = -1;
+    data = 0;
+}
+
+void MMap::print() {
+    DMESG("MMap %p r=%d len=%d fd=%d data=%p", this, refcnt, length, fd, data);
+}
+
+void MMap::destroy() {
+    munmap(data, length);
+    close(fd);
+}
+}
+
+namespace control {
+
+/** Create new file mapping in memory */
+//%
+MMap *mmap(String filename, int size, int offset) {
+    int fd = open(filename->data, O_RDWR, 0);
+    if (fd < 0)
+        return 0;
+
+    void *data = ::mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, offset);
+    if (data == MAP_FAILED) {
+        close(fd);
+        return 0;
+    }
+
+    auto r = new MMap();
+    r->fd = fd;
+    r->length = size;
+    r->data = (uint8_t*)data;
+    return r;
+}
+}
+
+namespace MMapMethods {
+
+/**
+ * Write a number in specified format in the buffer.
+ */
+//%
+void setNumber(MMap *buf, NumberFormat format, int offset, TNumber value) {
+    if (offset < 0)
+        return;
+    setNumberCore(buf->data + offset, buf->length - offset, format, value);
+}
+
+/**
+ * Read a number in specified format from the buffer.
+ */
+//%
+TNumber getNumber(MMap *buf, NumberFormat format, int offset) {
+    if (offset < 0)
+        return fromInt(0);
+    return getNumberCore(buf->data + offset, buf->length - offset, format);
+}
+
+/** Returns the length of a Buffer object. */
+//% property
+int length(MMap *s) {
+    return s->length;
+}
+}

libs/core/pxt.h

@@ -14,6 +14,20 @@ class Button;
 typedef Button *Button_;
 
 extern "C" void target_init();
+
+
+class MMap : public RefObject {
+  public:
+    int length;
+    int fd;
+    uint8_t *data;
+
+    MMap();
+    void destroy();
+    void print();
+};
+
+
 }
 
 #define DEVICE_EVT_ANY 0

libs/core/pxt.json

@@ -7,6 +7,7 @@
         "pxt.h",
         "pxtcore.h",
         "linux.cpp",
+        "mmap.cpp",
         "control.cpp",
         "buttons.cpp",
         "screen.cpp",

libs/core/shims.d.ts

@@ -1,4 +1,29 @@
 // Auto-generated. Do not edit.
+declare namespace control {
+
+    /** Create new file mapping in memory */
+    //% shim=control::mmap
+    function mmap(filename: string, size: int32, offset: int32): MMap;
+}
+
+
+declare interface MMap {
+    /**
+     * Write a number in specified format in the buffer.
+     */
+    //% shim=MMapMethods::setNumber
+    setNumber(format: NumberFormat, offset: int32, value: number): void;
+
+    /**
+     * Read a number in specified format from the buffer.
+     */
+    //% shim=MMapMethods::getNumber
+    getNumber(format: NumberFormat, offset: int32): number;
+
+    /** Returns the length of a Buffer object. */
+    //% property shim=MMapMethods::length
+    length: int32;
+}
 declare namespace control {
 
     /**