renamed function 'print' -> 'ToHexString'; this func returns std::string now

cpp/src/arrow/buffer.cc

@@ -18,7 +18,8 @@
 #include "arrow/buffer.h"
 
 #include <cstdint>
-#include <iostream>
+#include <iomanip>
+#include <sstream>
 #include <utility>
 
 #include "arrow/memory_pool.h"
@@ -48,13 +49,15 @@ Status Buffer::Copy(const int64_t start, const int64_t nbytes,
   return Copy(start, nbytes, default_memory_pool(), out);
 }
 
-void Buffer::print() {
+std::string Buffer::ToHexString() {
   const uint8_t* _data = is_mutable() ? mutable_data() : data();
+  std::stringstream ss;
 
   for (int64_t i = 0; i < size(); ++i) {
-    std::cout << std::hex << static_cast<unsigned int>(_data[i]);
+    ss << std::setfill('0') << std::setw(2) <<
+      std::hex << static_cast<unsigned int>(_data[i]);
   }
-  std::cout << std::endl;
+  return ss.str();
 }
 
 bool Buffer::Equals(const Buffer& other, const int64_t nbytes) const {

cpp/src/arrow/buffer.h

@@ -89,7 +89,7 @@ class ARROW_EXPORT Buffer {
 
   bool is_mutable() const { return is_mutable_; }
 
-  void print();
+  std::string ToHexString();
 
   /// Return true if both buffers are the same size and contain the same bytes
   /// up to the number of compared bytes

python/pyarrow/includes/libarrow.pxd

@@ -208,7 +208,7 @@ cdef extern from "arrow/api.h" namespace "arrow" nogil:
         int64_t size()
         shared_ptr[CBuffer] parent()
         c_bool is_mutable() const
-        void print()
+        c_string ToHexString()
         c_bool Equals(const CBuffer& other)
 
     shared_ptr[CBuffer] SliceBuffer(const shared_ptr[CBuffer]& buffer,

python/pyarrow/io.pxi

@@ -868,8 +868,8 @@ cdef class Buffer:
         """
         return <uintptr_t> self.buffer.get().data()
 
-    def print(self):
-        self.buffer.get().print()
+    def ToHexString(self):
+        return self.buffer.get().ToHexString()
 
     @property
     def is_mutable(self):