Add BinaryenModuleWriteSExpr to write a module to a string in s-expr format (#2106)

Fixes #2103.

4 files changed, 84 insertions, 0 deletions

diff --git a/src/binaryen-c.cpp b/src/binaryen-c.cpp
index 990612829..fb8b730c7 100644
--- a/src/binaryen-c.cpp
+++ b/src/binaryen-c.cpp
@@ -35,6 +35,8 @@
 #include "wasm-validator.h"
 #include "wasm.h"
 #include "wasm2js.h"
+#include <iostream>
+#include <sstream>
 
 #ifdef __EMSCRIPTEN__
 #include <emscripten.h>
@@ -3288,6 +3290,26 @@ BinaryenModuleWrite(BinaryenModuleRef module, char* output, size_t outputSize) {
     .outputBytes;
 }
 
+size_t BinaryenModuleWriteText(BinaryenModuleRef module,
+                               char* output,
+                               size_t outputSize) {
+
+  if (tracing) {
+    std::cout << "  // BinaryenModuleWriteTextr\n";
+  }
+
+  // use a stringstream as an std::ostream. Extract the std::string
+  // representation, and then store in the output.
+  std::stringstream ss;
+  WasmPrinter::printModule((Module*)module, ss);
+
+  const auto temp = ss.str();
+  const auto ctemp = temp.c_str();
+
+  strncpy(output, ctemp, outputSize);
+  return std::min(outputSize, temp.size());
+}
+
 BinaryenBufferSizes BinaryenModuleWriteWithSourceMap(BinaryenModuleRef module,
                                                      const char* url,
                                                      char* output,
@@ -3333,6 +3355,21 @@ BinaryenModuleAllocateAndWrite(BinaryenModuleRef module,
   return {binary, buffer.size(), sourceMap};
 }
 
+char* BinaryenModuleAllocateAndWriteText(BinaryenModuleRef* module) {
+  if (tracing) {
+    std::cout << " // BinaryenModuleAllocateAndWriteText(the_module);";
+  }
+
+  std::stringstream ss;
+  WasmPrinter::printModule((Module*)module, ss);
+
+  const std::string out = ss.str();
+  const int len = out.length() + 1;
+  char* cout = (char*)malloc(len);
+  strncpy(cout, out.c_str(), len);
+  return cout;
+}
+
 BinaryenModuleRef BinaryenModuleRead(char* input, size_t inputSize) {
   if (tracing) {
     std::cout << "  // BinaryenModuleRead\n";
diff --git a/src/binaryen-c.h b/src/binaryen-c.h
index e287e2541..ae6747cea 100644
--- a/src/binaryen-c.h
+++ b/src/binaryen-c.h
@@ -1012,6 +1012,13 @@ void BinaryenModuleAutoDrop(BinaryenModuleRef module);
 size_t
 BinaryenModuleWrite(BinaryenModuleRef module, char* output, size_t outputSize);
 
+// Serialize a module in s-expression text format.
+// @return how many bytes were written. This will be less than or equal to
+//         outputSize
+size_t BinaryenModuleWriteText(BinaryenModuleRef module,
+                               char* output,
+                               size_t outputSize);
+
 typedef struct BinaryenBufferSizes {
   size_t outputBytes;
   size_t sourceMapBytes;
@@ -1046,6 +1053,11 @@ BinaryenModuleAllocateAndWriteResult
 BinaryenModuleAllocateAndWrite(BinaryenModuleRef module,
                                const char* sourceMapUrl);
 
+// Serialize a module in s-expression form. Implicity allocates the returned
+// char* with malloc(), and expects the user to free() them manually
+// once not needed anymore.
+char* BinaryenModuleAllocateAndWriteText(BinaryenModuleRef* module);
+
 // Deserialize a module from binary form.
 BinaryenModuleRef BinaryenModuleRead(char* input, size_t inputSize);
 
diff --git a/test/example/c-api-kitchen-sink.c b/test/example/c-api-kitchen-sink.c
index 0efafde52..43069c865 100644
--- a/test/example/c-api-kitchen-sink.c
+++ b/test/example/c-api-kitchen-sink.c
@@ -785,6 +785,19 @@ void test_binaries() {
   assert(BinaryenModuleValidate(module));
   printf("module loaded from binary form:\n");
   BinaryenModulePrint(module);
+
+  // write the s-expr representation of the module.
+  BinaryenModuleWriteText(module, buffer, 1024);
+  printf("module s-expr printed (in memory):\n%s\n", buffer);
+
+
+  // writ the s-expr representation to a pointer which is managed by the
+  // caller
+  char *text = BinaryenModuleAllocateAndWriteText(module);
+  printf("module s-expr printed (in memory, caller-owned):\n%s\n", text);
+  free(text);
+
+
   BinaryenModuleDispose(module);
 }
 
diff --git a/test/example/c-api-kitchen-sink.txt b/test/example/c-api-kitchen-sink.txt
index 5a4055ddb..f1eba84b7 100644
--- a/test/example/c-api-kitchen-sink.txt
+++ b/test/example/c-api-kitchen-sink.txt
@@ -1875,6 +1875,28 @@ module loaded from binary form:
   )
  )
 )
+module s-expr printed (in memory):
+(module
+ (type $0 (func (param i32 i32) (result i32)))
+ (func $adder (; 0 ;) (type $0) (param $0 i32) (param $1 i32) (result i32)
+  (i32.add
+   (local.get $0)
+   (local.get $1)
+  )
+ )
+)
+
+module s-expr printed (in memory, caller-owned):
+(module
+ (type $0 (func (param i32 i32) (result i32)))
+ (func $adder (; 0 ;) (type $0) (param $0 i32) (param $1 i32) (result i32)
+  (i32.add
+   (local.get $0)
+   (local.get $1)
+  )
+ )
+)
+
 (module
  (type $vi (func (param i32)))
  (type $v (func))