first demo working!

examples/python-interop/demo.c

@@ -0,0 +1,252 @@
+#include <errno.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdalign.h>
+#include <Python.h>
+
+void *roc_alloc(size_t size, unsigned int alignment) 
+{ 
+    return malloc(size); 
+}
+
+void *roc_realloc(void *ptr, size_t new_size, size_t old_size,
+                  unsigned int alignment)
+{
+    return realloc(ptr, new_size);
+}
+
+void roc_dealloc(void *ptr, unsigned int alignment) { free(ptr); }
+
+__attribute__((noreturn)) void roc_panic(void *ptr, unsigned int alignment)
+{
+    /* b_raise(rb_eException, "%s", (char *)ptr); */
+    PyErr_SetString(PyExc_RuntimeError, (char *)ptr);
+}
+
+void *roc_memcpy(void *dest, const void *src, size_t n)
+{
+    return memcpy(dest, src, n);
+}
+
+void *roc_memset(void *str, int c, size_t n) { return memset(str, c, n); }
+
+// Reference counting
+
+// If the refcount is set to this, that means the allocation is
+// stored in readonly memory in the binary, and we must not
+// attempt to increment or decrement it; if we do, we'll segfault!
+const ssize_t REFCOUNT_READONLY = 0;
+const ssize_t REFCOUNT_ONE = (ssize_t)PTRDIFF_MIN;
+const size_t MASK = (size_t)PTRDIFF_MIN;
+
+// Increment reference count, given a pointer to the first element in a collection.
+// We don't need to check for overflow because in order to overflow a usize worth of refcounts,
+// you'd need to somehow have more pointers in memory than the OS's virtual address space can hold.
+void incref(uint8_t* bytes, uint32_t alignment)
+{
+    ssize_t *refcount_ptr = ((ssize_t *)bytes) - 1;
+    ssize_t refcount = *refcount_ptr;
+
+    if (refcount != REFCOUNT_READONLY) {
+        *refcount_ptr = refcount + 1;
+    }
+}
+
+// Decrement reference count, given a pointer to the first element in a collection.
+// Then call roc_dealloc if nothing is referencing this collection anymore.
+void decref(uint8_t* bytes, uint32_t alignment)
+{
+    if (bytes == NULL) {
+        return;
+    }
+
+    size_t extra_bytes = (sizeof(size_t) >= (size_t)alignment) ? sizeof(size_t) : (size_t)alignment;
+    ssize_t *refcount_ptr = ((ssize_t *)bytes) - 1;
+    ssize_t refcount = *refcount_ptr;
+
+    if (refcount != REFCOUNT_READONLY) {
+        *refcount_ptr = refcount - 1;
+
+        if (refcount == REFCOUNT_ONE) {
+            void *original_allocation = (void *)(refcount_ptr - (extra_bytes - sizeof(size_t)));
+
+            roc_dealloc(original_allocation, alignment);
+        }
+    }
+}
+
+// RocBytes (List U8)
+
+struct RocBytes
+{
+    uint8_t *bytes;
+    size_t len;
+    size_t capacity;
+};
+
+struct RocBytes init_rocbytes(uint8_t *bytes, size_t len)
+{
+    if (len == 0)
+    {
+        struct RocBytes ret = {
+            .len = 0,
+            .bytes = NULL,
+            .capacity = MASK,
+        };
+
+        return ret;
+    }
+    else
+    {
+        struct RocBytes ret;
+        size_t refcount_size = sizeof(size_t);
+        uint8_t *new_content = ((uint8_t *)roc_alloc(len + refcount_size, alignof(size_t))) + refcount_size;
+
+        memcpy(new_content, bytes, len);
+
+        ret.bytes = new_content;
+        ret.len = len;
+        ret.capacity = len;
+
+        return ret;
+    }
+}
+
+// RocStr
+
+struct RocStr
+{
+    uint8_t *bytes;
+    size_t len;
+    size_t capacity;
+};
+
+struct RocStr init_rocstr(uint8_t *bytes, size_t len)
+{
+    if (len == 0)
+    {
+        struct RocStr ret = {
+            .len = 0,
+            .bytes = NULL,
+            .capacity = MASK,
+        };
+
+        return ret;
+    }
+    else if (len < sizeof(struct RocStr))
+    {
+        // Start out with zeroed memory, so that
+        // if we end up comparing two small RocStr values
+        // for equality, we won't risk memory garbage resulting
+        // in two equal strings appearing unequal.
+        struct RocStr ret = {
+            .len = 0,
+            .bytes = NULL,
+            .capacity = MASK,
+        };
+
+        // Copy the bytes into the stack allocation
+        memcpy(&ret, bytes, len);
+
+        // Record the string's length in the last byte of the stack allocation
+        ((uint8_t *)&ret)[sizeof(struct RocStr) - 1] = (uint8_t)len | 0b10000000;
+
+        return ret;
+    }
+    else
+    {
+        // A large RocStr is the same as a List U8 (aka RocBytes) in memory.
+        struct RocBytes roc_bytes = init_rocbytes(bytes, len);
+
+        struct RocStr ret = {
+            .len = roc_bytes.len,
+            .bytes = roc_bytes.bytes,
+            .capacity = roc_bytes.capacity,
+        };
+
+        return ret;
+    }
+}
+
+bool is_small_str(struct RocStr str) { return ((ssize_t)str.capacity) < 0; }
+
+// Determine the length of the string, taking into
+// account the small string optimization
+size_t roc_str_len(struct RocStr str)
+{
+    uint8_t *bytes = (uint8_t *)&str;
+    uint8_t last_byte = bytes[sizeof(str) - 1];
+    uint8_t last_byte_xored = last_byte ^ 0b10000000;
+    size_t small_len = (size_t)(last_byte_xored);
+    size_t big_len = str.len;
+
+    // Avoid branch misprediction costs by always
+    // determining both small_len and big_len,
+    // so this compiles to a cmov instruction.
+    if (is_small_str(str))
+    {
+        return small_len;
+    }
+    else
+    {
+        return big_len;
+    }
+}
+
+extern void roc__mainForHost_1_exposed_generic(struct RocBytes *ret, struct RocBytes *arg);
+
+// Receive a value from Python, JSON serialized it and pass it to Roc as a List U8
+// (at which point the Roc platform will decode it and crash if it's invalid,
+// which roc_panic will translate into a Python exception), then get some JSON back from Roc
+// - also as a List U8 - and have Python JSON.parse it into a plain Python value to return.
+PyObject * call_roc(PyObject *self, PyObject *args)
+{
+    int num;
+
+    if(!PyArg_ParseTuple(args, "i", &num)) {
+        return NULL;
+    }
+
+
+    char str_num[64] = {0};
+    sprintf(str_num, "%d", num);
+
+    // Turn the given Python number into a JSON string.
+    struct RocBytes arg = init_rocbytes((uint8_t *)str_num, strlen(str_num));
+    struct RocBytes ret;
+
+    // Call the Roc function to populate `ret`'s bytes.
+    roc__mainForHost_1_exposed_generic(&ret, &arg);
+
+    // Create a Python string from the heap-allocated JSON bytes the Roc function returned.
+    PyObject* py_str = PyUnicode_FromString((char*)ret.bytes);
+    if (py_str == NULL) {
+        return NULL;
+    }
+
+    // Now that we've created py_str, we're no longer referencing the RocBytes.
+    decref((void *)&ret, alignof(uint8_t *));
+
+    return Py_BuildValue("O", py_str);
+}
+
+static PyMethodDef DemoMethods[] = {
+    {"call_roc", call_roc, METH_VARARGS, "pooop"},
+    {NULL, NULL, 0, NULL}
+};
+
+static struct PyModuleDef demoModule = {
+    PyModuleDef_HEAD_INIT,
+    "call_roc",
+    "test roc call",
+    -1,
+    DemoMethods
+};
+
+PyMODINIT_FUNC PyInit_demo(void) {
+    return PyModule_Create(&demoModule);
+}