Add ability to initialize Pl_Function with a C-style function

include/qpdf/Pl_Function.hh

@@ -31,6 +31,9 @@
 //
 // It is okay to not call finish() on this pipeline if it has no
 // "next".
+//
+// It is okay to keep calling write() after a previous write throws an
+// exception as long as the delegated function allows it.
 
 #include <qpdf/Pipeline.hh>
 
@@ -41,8 +44,26 @@ class QPDF_DLL_CLASS Pl_Function: public Pipeline
   public:
     typedef std::function<void(unsigned char const*, size_t)> writer_t;
 
+    // The supplied function is called every time write is called.
     QPDF_DLL
     Pl_Function(char const* identifier, Pipeline* next, writer_t fn);
+
+    // The supplied C-style function is called every time write is
+    // called. The udata option is passed into the function with each
+    // call. If the function returns a non-zero value, a runtime error
+    // is thrown.
+    typedef int (*writer_c_t)(unsigned char const*, size_t, void*);
+    QPDF_DLL
+    Pl_Function(
+        char const* identifier, Pipeline* next, writer_c_t fn, void* udata);
+    typedef int (*writer_c_char_t)(char const*, size_t, void*);
+    QPDF_DLL
+    Pl_Function(
+        char const* identifier,
+        Pipeline* next,
+        writer_c_char_t fn,
+        void* udata);
+
     QPDF_DLL
     virtual ~Pl_Function();
 

libqpdf/Pl_Function.cc

@@ -15,6 +15,36 @@ Pl_Function::Pl_Function(char const* identifier, Pipeline* next, writer_t fn) :
 {
 }
 
+Pl_Function::Pl_Function(
+    char const* identifier, Pipeline* next, writer_c_t fn, void* udata) :
+    Pipeline(identifier, next),
+    m(new Members(nullptr))
+{
+    m->fn = [identifier, fn, udata](unsigned char const* data, size_t len) {
+        int code = fn(data, len, udata);
+        if (code != 0) {
+            throw std::runtime_error(
+                std::string(identifier) + " function returned code " +
+                QUtil::int_to_string(code));
+        }
+    };
+}
+
+Pl_Function::Pl_Function(
+    char const* identifier, Pipeline* next, writer_c_char_t fn, void* udata) :
+    Pipeline(identifier, next),
+    m(new Members(nullptr))
+{
+    m->fn = [identifier, fn, udata](unsigned char const* data, size_t len) {
+        int code = fn(reinterpret_cast<char const*>(data), len, udata);
+        if (code != 0) {
+            throw std::runtime_error(
+                std::string(identifier) + " function returned code " +
+                QUtil::int_to_string(code));
+        }
+    };
+}
+
 Pl_Function::~Pl_Function()
 {
     // Must be explicit and not inline -- see QPDF_DLL_CLASS in

libtests/pl_function.cc

@@ -5,6 +5,38 @@
 #include <qpdf/Pl_String.hh>
 #include <iostream>
 
+namespace
+{
+    struct Count
+    {
+        int count{0};
+    };
+} // namespace
+
+int
+f(unsigned char const* data, size_t len, void* udata)
+{
+    auto c = reinterpret_cast<Count*>(udata);
+    ++c->count;
+    std::cout << "got " << data << "(" << len << ")" << std::endl;
+    if (c->count == 3) {
+        return 1;
+    }
+    return 0;
+}
+
+int
+g(char const* data, size_t len, void* udata)
+{
+    auto c = reinterpret_cast<Count*>(udata);
+    ++c->count;
+    std::cout << "signed got " << data << "(" << len << ")" << std::endl;
+    if (c->count == 2) {
+        return 2;
+    }
+    return 0;
+}
+
 int
 main(int argc, char* argv[])
 {
@@ -23,5 +55,32 @@ main(int argc, char* argv[])
     p2.finish();
     assert(s == "c2FsYWQ=");
 
+    Count c;
+    Pl_Function p3("c-function", nullptr, f, &c);
+    p3 << "one";
+    p3 << "two";
+    try {
+        p3 << "three";
+        assert(false);
+    } catch (std::runtime_error& e) {
+        std::cout << "three threw " << e.what() << std::endl;
+    }
+    p3 << "four";
+    p3.finish();
+    assert(c.count == 4);
+
+    c.count = 0;
+    Pl_Function p4("c-function", nullptr, g, &c);
+    p4 << "potato";
+    try {
+        p4 << "salad";
+        assert(false);
+    } catch (std::runtime_error& e) {
+        std::cout << "salad threw " << e.what() << std::endl;
+    }
+    p4 << "quack";
+    p4.finish();
+    assert(c.count == 3);
+
     return 0;
 }

libtests/qtest/pl_function/exp

@@ -1,2 +1,11 @@
 p1: 6: potato
 p2: 5: salad
+got one(3)
+got two(3)
+got three(5)
+three threw c-function function returned code 1
+got four(4)
+signed got potato(6)
+signed got salad(5)
+salad threw c-function function returned code 2
+signed got quack(5)