Adjust the C and Zig examples

Author: arnaudgolfouse

examples/hello_c/hello.c

@@ -4,23 +4,37 @@
 #include <cstddef>
 #include <cstdint>
 #include <cstdlib>
+#include <cstring>
 #define PROTOCOL_FUNCTION __attribute__((import_module("typst_env"))) extern "C"
 #else
 #include <stddef.h>
 #include <stdint.h>
 #include <stdlib.h>
+#include <string.h>
 #define PROTOCOL_FUNCTION __attribute__((import_module("typst_env"))) extern
 #endif
 
+// ===
+// Functions for the protocol
+
 PROTOCOL_FUNCTION void
 wasm_minimal_protocol_send_result_to_host(const uint8_t *ptr, size_t len);
 PROTOCOL_FUNCTION void wasm_minimal_protocol_write_args_to_buffer(uint8_t *ptr);
 
+EMSCRIPTEN_KEEPALIVE void wasm_minimal_protocol_free_byte_buffer(uint8_t *ptr,
+                                                                 size_t len) {
+  free(ptr);
+}
+
+// ===
+
 EMSCRIPTEN_KEEPALIVE
 int32_t hello(void) {
-  const char message[] = "Hello world !";
-  wasm_minimal_protocol_send_result_to_host((uint8_t *)message,
-                                            sizeof(message) - 1);
+  const char static_message[] = "Hello world !";
+  const size_t length = sizeof(static_message);
+  char *message = malloc(length);
+  memcpy((void *)message, (void *)static_message, length);
+  wasm_minimal_protocol_send_result_to_host((uint8_t *)message, length - 1);
   return 0;
 }
 
@@ -36,7 +50,6 @@ int32_t double_it(size_t arg_len) {
     alloc_result[arg_len + i] = alloc_result[i];
   }
   wasm_minimal_protocol_send_result_to_host(alloc_result, result_len);
-  free(alloc_result);
   return 0;
 }
 
@@ -66,7 +79,6 @@ int32_t concatenate(size_t arg1_len, size_t arg2_len) {
 
   wasm_minimal_protocol_send_result_to_host(result, total_len + 1);
 
-  free(result);
   free(args);
   return 0;
 }
@@ -102,24 +114,27 @@ int32_t shuffle(size_t arg1_len, size_t arg2_len, size_t arg3_len) {
 
   wasm_minimal_protocol_send_result_to_host(result, result_len);
 
-  free(result);
   free(args);
   return 0;
 }
 
 EMSCRIPTEN_KEEPALIVE
 int32_t returns_ok() {
-  const char message[] = "This is an `Ok`";
-  wasm_minimal_protocol_send_result_to_host((uint8_t *)message,
-                                            sizeof(message) - 1);
+  const char static_message[] = "This is an `Ok`";
+  const size_t length = sizeof(static_message);
+  char *message = malloc(length);
+  memcpy((void *)message, (void *)static_message, length);
+  wasm_minimal_protocol_send_result_to_host((uint8_t *)message, length - 1);
   return 0;
 }
 
 EMSCRIPTEN_KEEPALIVE
 int32_t returns_err() {
-  const char message[] = "This is an `Err`";
-  wasm_minimal_protocol_send_result_to_host((uint8_t *)message,
-                                            sizeof(message) - 1);
+  const char static_message[] = "This is an `Err`";
+  const size_t length = sizeof(static_message);
+  char *message = malloc(length);
+  memcpy((void *)message, (void *)static_message, length);
+  wasm_minimal_protocol_send_result_to_host((uint8_t *)message, length - 1);
   return 1;
 }
 

examples/hello_zig/hello.zig

@@ -1,23 +1,36 @@
 const std = @import("std");
 const allocator = std.heap.page_allocator;
 
+// ===
+// Functions for the protocol
+
 extern "typst_env" fn wasm_minimal_protocol_send_result_to_host(ptr: [*]const u8, len: usize) void;
 extern "typst_env" fn wasm_minimal_protocol_write_args_to_buffer(ptr: [*]u8) void;
 
+export fn wasm_minimal_protocol_free_byte_buffer(ptr: [*]u8, len: usize) void {
+    var slice: []u8 = undefined;
+    slice.ptr = ptr;
+    slice.len = len;
+    allocator.free(slice);
+}
+
+// ===
+
 export fn hello() i32 {
     const message = "Hello world !";
-    wasm_minimal_protocol_send_result_to_host(message.ptr, message.len);
+    var result = allocator.alloc(u8, message.len) catch return 1;
+    @memcpy(result, message);
+    wasm_minimal_protocol_send_result_to_host(result.ptr, result.len);
     return 0;
 }
 
 export fn double_it(arg1_len: usize) i32 {
-    var alloc_result = allocator.alloc(u8, arg1_len * 2) catch return 1;
-    defer allocator.free(alloc_result);
-    wasm_minimal_protocol_write_args_to_buffer(alloc_result.ptr);
+    var result = allocator.alloc(u8, arg1_len * 2) catch return 1;
+    wasm_minimal_protocol_write_args_to_buffer(result.ptr);
     for (0..arg1_len) |i| {
-        alloc_result[i + arg1_len] = alloc_result[i];
+        result[i + arg1_len] = result[i];
     }
-    wasm_minimal_protocol_send_result_to_host(alloc_result.ptr, alloc_result.len);
+    wasm_minimal_protocol_send_result_to_host(result.ptr, result.len);
     return 0;
 }
 
@@ -27,7 +40,6 @@ export fn concatenate(arg1_len: usize, arg2_len: usize) i32 {
     wasm_minimal_protocol_write_args_to_buffer(args.ptr);
 
     var result = allocator.alloc(u8, arg1_len + arg2_len + 1) catch return 1;
-    defer allocator.free(result);
     for (0..arg1_len) |i| {
         result[i] = args[i];
     }
@@ -49,27 +61,30 @@ export fn shuffle(arg1_len: usize, arg2_len: usize, arg3_len: usize) i32 {
     var arg2 = args[arg1_len .. arg1_len + arg2_len];
     var arg3 = args[arg1_len + arg2_len .. args.len];
 
-    var result: std.ArrayList(u8) = std.ArrayList(u8).initCapacity(allocator, args_len + 2) catch return 1;
-    defer result.deinit();
-    result.appendSlice(arg3) catch return 1;
-    result.append('-') catch return 1;
-    result.appendSlice(arg1) catch return 1;
-    result.append('-') catch return 1;
-    result.appendSlice(arg2) catch return 1;
+    var result = allocator.alloc(u8, arg1_len + arg2_len + arg3_len + 2) catch return 1;
+    @memcpy(result[0..arg3.len], arg3);
+    result[arg3.len] = '-';
+    @memcpy(result[arg3.len + 1 ..][0..arg1.len], arg1);
+    result[arg3.len + arg1.len + 1] = '-';
+    @memcpy(result[arg3.len + arg1.len + 2 ..][0..arg2.len], arg2);
 
-    wasm_minimal_protocol_send_result_to_host(result.items.ptr, result.items.len);
+    wasm_minimal_protocol_send_result_to_host(result.ptr, result.len);
     return 0;
 }
 
 export fn returns_ok() i32 {
     const message = "This is an `Ok`";
-    wasm_minimal_protocol_send_result_to_host(message.ptr, message.len);
+    var result = allocator.alloc(u8, message.len) catch return 1;
+    @memcpy(result, message);
+    wasm_minimal_protocol_send_result_to_host(result.ptr, result.len);
     return 0;
 }
 
 export fn returns_err() i32 {
     const message = "This is an `Err`";
-    wasm_minimal_protocol_send_result_to_host(message.ptr, message.len);
+    var result = allocator.alloc(u8, message.len) catch return 1;
+    @memcpy(result, message);
+    wasm_minimal_protocol_send_result_to_host(result.ptr, result.len);
     return 1;
 }