diff --git a/libopenfpga/libpcf/CMakeLists.txt b/libopenfpga/libpcf/CMakeLists.txt
new file mode 100644
index 000000000..8287bb3bc
--- /dev/null
+++ b/libopenfpga/libpcf/CMakeLists.txt
@@ -0,0 +1,35 @@
+cmake_minimum_required(VERSION 3.9)
+
+project("libpcf")
+
+file(GLOB_RECURSE EXEC_SOURCES test/*.cpp)
+file(GLOB_RECURSE LIB_SOURCES src/*.cpp)
+file(GLOB_RECURSE LIB_HEADERS src/*.h)
+files_to_dirs(LIB_HEADERS LIB_INCLUDE_DIRS)
+
+#Remove test executable from library
+list(REMOVE_ITEM LIB_SOURCES ${EXEC_SOURCES})
+
+#Create the library
+add_library(libpcf STATIC
+            ${LIB_HEADERS}
+            ${LIB_SOURCES})
+target_include_directories(libpcf PUBLIC ${LIB_INCLUDE_DIRS})
+set_target_properties(libpcf PROPERTIES PREFIX "") #Avoid extra 'lib' prefix
+
+#Specify link-time dependancies
+target_link_libraries(libpcf
+                      libopenfpgautil
+                      libarchopenfpga
+                      libvtrutil
+                      libpugixml
+                      libpugiutil)
+
+#Create the test executable
+foreach(testsourcefile ${EXEC_SOURCES})
+    # Use a simple string replace, to cut off .cpp.
+    get_filename_component(testname ${testsourcefile} NAME_WE)
+    add_executable(${testname} ${testsourcefile})
+    # Make sure the library is linked to each test executable
+    target_link_libraries(${testname} libpcf)
+endforeach(testsourcefile ${EXEC_SOURCES})
diff --git a/libopenfpga/libpcf/example/fpga_io_nets.xml b/libopenfpga/libpcf/example/fpga_io_nets.xml
new file mode 100644
index 000000000..90523a274
--- /dev/null
+++ b/libopenfpga/libpcf/example/fpga_io_nets.xml
@@ -0,0 +1,9 @@
+<pin_constraints>
+  <!-- For a given .blif file, we want to assign 
+       - the clk0 signal to the clk[0] port of the FPGA fabric
+       - the clk1 signal to the clk[1] port of the FPGA fabric
+    -->
+  <set_io pin="clk[0]" net="clk0"/>
+  <set_io pin="clk[1]" net="clk1"/>
+</pin_constraints>
+
diff --git a/libopenfpga/libpcf/src/pin_constraints.cpp b/libopenfpga/libpcf/src/pin_constraints.cpp
new file mode 100644
index 000000000..4f7a701a7
--- /dev/null
+++ b/libopenfpga/libpcf/src/pin_constraints.cpp
@@ -0,0 +1,72 @@
+#include <algorithm>
+
+#include "vtr_assert.h"
+#include "vtr_log.h"
+
+#include "pin_constraints.h"
+
+/************************************************************************
+ * Member functions for class PinConstraints
+ ***********************************************************************/
+
+/************************************************************************
+ * Constructors
+ ***********************************************************************/
+PinConstraints::PinConstraints() {
+  return;
+}
+
+/************************************************************************
+ * Public Accessors : aggregates
+ ***********************************************************************/
+PinConstraints::pin_constraint_range PinConstraints::pin_constraints() const {
+  return vtr::make_range(pin_constraint_ids_.begin(), pin_constraint_ids_.end());
+}
+
+/************************************************************************
+ * Public Accessors : Basic data query 
+ ***********************************************************************/
+openfpga::BasicPort PinConstraints::pin(const PinConstraintId& pin_constraint_id) const {
+  /* validate the pin_constraint_id */
+  VTR_ASSERT(valid_pin_constraint_id(pin_constraint_id));
+  return pin_constraint_pins_[pin_constraint_id]; 
+}
+
+std::string PinConstraints::net(const PinConstraintId& pin_constraint_id) const {
+  /* validate the pin_constraint_id */
+  VTR_ASSERT(valid_pin_constraint_id(pin_constraint_id));
+  return pin_constraint_nets_[pin_constraint_id]; 
+}
+
+bool PinConstraints::empty() const {
+  return 0 == pin_constraint_ids_.size();
+}
+
+/************************************************************************
+ * Public Mutators
+ ***********************************************************************/
+void PinConstraints::reserve_pin_constraints(const size_t& num_pin_constraints) {
+  pin_constraint_ids_.reserve(num_pin_constraints);
+  pin_constraint_pins_.reserve(num_pin_constraints);
+  pin_constraint_nets_.reserve(num_pin_constraints);
+}
+
+PinConstraintId PinConstraints::create_pin_constraint(const openfpga::BasicPort& pin,
+                                                      const std::string& net) {
+  /* Create a new id */
+  PinConstraintId pin_constraint_id = PinConstraintId(pin_constraint_ids_.size());
+  
+  pin_constraint_ids_.push_back(pin_constraint_id);
+  pin_constraint_pins_.push_back(pin);
+  pin_constraint_nets_.push_back(net);
+  
+  return pin_constraint_id;
+}
+
+/************************************************************************
+ * Internal invalidators/validators 
+ ***********************************************************************/
+/* Validators */
+bool PinConstraints::valid_pin_constraint_id(const PinConstraintId& pin_constraint_id) const {
+  return ( size_t(pin_constraint_id) < pin_constraint_ids_.size() ) && ( pin_constraint_id == pin_constraint_ids_[pin_constraint_id] ); 
+}
diff --git a/libopenfpga/libpcf/src/pin_constraints.h b/libopenfpga/libpcf/src/pin_constraints.h
new file mode 100644
index 000000000..487eec22a
--- /dev/null
+++ b/libopenfpga/libpcf/src/pin_constraints.h
@@ -0,0 +1,77 @@
+#ifndef PIN_CONSTRAINTS_H
+#define PIN_CONSTRAINTS_H
+
+/********************************************************************
+ * This file include the declaration of pin constraints
+ *******************************************************************/
+#include <string>
+#include <map>
+#include <array>
+
+/* Headers from vtrutil library */
+#include "vtr_vector.h"
+#include "vtr_geometry.h"
+
+/* Headers from openfpgautil library */
+#include "openfpga_port.h"
+
+#include "pin_constraints_fwd.h"
+
+/********************************************************************
+ * A data structure to describe the pin constraints for FPGA fabrics
+ * This data structure may include a number of pin constraints
+ * each of which may constrain:
+ * - pin assignment, for instance, force a net to be mapped to specific pin
+ *
+ * Typical usage:
+ * --------------
+ *   // Create an object of pin constraints
+ *   PinConstraints pin_constraints;
+ *   // Add a pin assignment
+ *   openfpga::BasicPort pin_info(clk, 1);
+ *   std::string net_info("top_clock");
+ *   PinConstraintId pin_constraint_id = pin_constraints.create_pin_constraint(pin_info, net_info);
+ *
+ *******************************************************************/
+class PinConstraints {
+  public: /* Types */
+    typedef vtr::vector<PinConstraintId, PinConstraintId>::const_iterator pin_constraint_iterator;
+    /* Create range */
+    typedef vtr::Range<pin_constraint_iterator> pin_constraint_range;
+  public:  /* Constructors */
+    PinConstraints();
+  public: /* Accessors: aggregates */
+    pin_constraint_range pin_constraints() const;
+  public: /* Public Accessors: Basic data query */
+    /* Get the pin to be constrained */
+    openfpga::BasicPort pin(const PinConstraintId& pin_constraint_id) const;
+
+    /* Get the net to be constrained */
+    std::string net(const PinConstraintId& pin_constraint_id) const;
+
+    /* Check if there are any pin constraints */
+    bool empty() const;
+
+  public: /* Public Mutators */
+
+    /* Reserve a number of design constraints to be memory efficent */
+    void reserve_pin_constraints(const size_t& num_pin_constraints);
+
+    /* Add a pin constraint to storage */
+    PinConstraintId create_pin_constraint(const openfpga::BasicPort& pin,
+                                          const std::string& net);
+
+  public: /* Public invalidators/validators */
+    bool valid_pin_constraint_id(const PinConstraintId& pin_constraint_id) const;
+  private: /* Internal data */
+    /* Unique ids for each design constraint */
+    vtr::vector<PinConstraintId, PinConstraintId> pin_constraint_ids_;
+
+    /* Pins to constraint */
+    vtr::vector<PinConstraintId, openfpga::BasicPort> pin_constraint_pins_;
+
+    /* Nets to constraint */
+    vtr::vector<PinConstraintId, std::string> pin_constraint_nets_;
+};
+
+#endif
diff --git a/libopenfpga/libpcf/src/pin_constraints_fwd.h b/libopenfpga/libpcf/src/pin_constraints_fwd.h
new file mode 100644
index 000000000..245e72ff3
--- /dev/null
+++ b/libopenfpga/libpcf/src/pin_constraints_fwd.h
@@ -0,0 +1,22 @@
+/************************************************************************
+ * A header file for PinConstraints class, including critical data declaration
+ * Please include this file only for using any PinConstraints data structure
+ * Refer to pin_constraints.h for more details 
+ ***********************************************************************/
+
+/************************************************************************
+ * Create strong id for PinConstraints to avoid illegal type casting 
+ ***********************************************************************/
+#ifndef PIN_CONSTRAINTS_FWD_H
+#define PIN_CONSTRAINTS_FWD_H
+
+#include "vtr_strong_id.h"
+
+struct pin_constraint_id_tag;
+
+typedef vtr::StrongId<pin_constraint_id_tag> PinConstraintId;
+
+/* Short declaration of class */
+class PinConstraints;
+
+#endif
diff --git a/libopenfpga/libpcf/src/read_xml_pin_constraints.cpp b/libopenfpga/libpcf/src/read_xml_pin_constraints.cpp
new file mode 100644
index 000000000..b0c662da5
--- /dev/null
+++ b/libopenfpga/libpcf/src/read_xml_pin_constraints.cpp
@@ -0,0 +1,82 @@
+/********************************************************************
+ * This file includes the top-level function of this library
+ * which reads an XML of pin constraints to the associated
+ * data structures
+ *******************************************************************/
+#include <string>
+
+/* Headers from pugi XML library */
+#include "pugixml.hpp"
+#include "pugixml_util.hpp"
+
+/* Headers from vtr util library */
+#include "vtr_assert.h"
+#include "vtr_time.h"
+
+/* Headers from libopenfpga util library */
+#include "openfpga_port_parser.h"
+
+/* Headers from libarchfpga */
+#include "arch_error.h"
+#include "read_xml_util.h"
+
+#include "read_xml_pin_constraints.h"
+
+/********************************************************************
+ * Parse XML codes of a <set_io> to an object of PinConstraint
+ *******************************************************************/
+static 
+void read_xml_pin_constraint(pugi::xml_node& xml_pin_constraint,
+                             const pugiutil::loc_data& loc_data,
+                             PinConstraints& pin_constraints) {
+
+  openfpga::PortParser port_parser(get_attribute(xml_pin_constraint, "pin", loc_data).as_string());
+
+  std::string net_name = get_attribute(xml_pin_constraint, "net", loc_data).as_string();
+
+  /* Create a new pin constraint in the storage */
+  PinConstraintId pin_constraint_id = pin_constraints.create_pin_constraint(port_parser.port(), net_name);
+
+  if (false == pin_constraints.valid_pin_constraint_id(pin_constraint_id)) {
+    archfpga_throw(loc_data.filename_c_str(), loc_data.line(xml_pin_constraint),
+                   "Fail to create pin constraint!\n");
+  }
+}
+
+/********************************************************************
+ * Parse XML codes about <pin_constraints> to an object of PinConstraints
+ *******************************************************************/
+PinConstraints read_xml_pin_constraints(const char* pin_constraint_fname) {
+
+  vtr::ScopedStartFinishTimer timer("Read Pin Constraints");
+
+  PinConstraints pin_constraints;
+
+  /* Parse the file */
+  pugi::xml_document doc;
+  pugiutil::loc_data loc_data;
+
+  try {
+    loc_data = pugiutil::load_xml(doc, pin_constraint_fname);
+
+    pugi::xml_node xml_root = get_single_child(doc, "pin_constraints", loc_data);
+
+    size_t num_pin_constraints = std::distance(xml_root.children().begin(), xml_root.children().end());
+    /* Reserve memory space for the region */
+    pin_constraints.reserve_pin_constraints(num_pin_constraints);
+
+    for (pugi::xml_node xml_pin_constraint : xml_root.children()) {
+      /* Error out if the XML child has an invalid name! */
+      if (xml_pin_constraint.name() != std::string("set_io")) {
+        bad_tag(xml_pin_constraint, loc_data, xml_root, {"set_io"});
+      }
+      read_xml_pin_constraint(xml_pin_constraint, loc_data, pin_constraints);
+    } 
+  } catch (pugiutil::XmlError& e) {
+    archfpga_throw(pin_constraint_fname, e.line(),
+                   "%s", e.what());
+  }
+
+  return pin_constraints; 
+}
+
diff --git a/libopenfpga/libpcf/src/read_xml_pin_constraints.h b/libopenfpga/libpcf/src/read_xml_pin_constraints.h
new file mode 100644
index 000000000..45065be26
--- /dev/null
+++ b/libopenfpga/libpcf/src/read_xml_pin_constraints.h
@@ -0,0 +1,16 @@
+#ifndef READ_XML_PIN_CONSTRAINTS_H
+#define READ_XML_PIN_CONSTRAINTS_H
+
+/********************************************************************
+ * Include header files that are required by function declaration
+ *******************************************************************/
+#include "pugixml_util.hpp"
+#include "pugixml.hpp"
+#include "pin_constraints.h"
+
+/********************************************************************
+ * Function declaration
+ *******************************************************************/
+PinConstraints read_xml_pin_constraints(const char* pin_constraint_fname);
+
+#endif
diff --git a/libopenfpga/libpcf/src/write_xml_pin_constraints.cpp b/libopenfpga/libpcf/src/write_xml_pin_constraints.cpp
new file mode 100644
index 000000000..ba471fb0c
--- /dev/null
+++ b/libopenfpga/libpcf/src/write_xml_pin_constraints.cpp
@@ -0,0 +1,94 @@
+/********************************************************************
+ * This file includes functions that outputs a pin constraint object to XML format
+ *******************************************************************/
+/* Headers from system goes first */
+#include <string>
+#include <algorithm>
+
+/* Headers from vtr util library */
+#include "vtr_assert.h"
+#include "vtr_log.h"
+#include "vtr_time.h"
+
+/* Headers from openfpga util library */
+#include "openfpga_digest.h"
+
+/* Headers from arch openfpga library */
+#include "write_xml_utils.h" 
+
+/* Headers from pin constraint library */
+#include "write_xml_pin_constraints.h"
+
+/********************************************************************
+ * A writer to output a pin constraint to XML format
+ *
+ * Return 0 if successful
+ * Return 1 if there are more serious bugs in the architecture 
+ * Return 2 if fail when creating files
+ *******************************************************************/
+static 
+int write_xml_io_constraint(std::fstream& fp,
+                            const PinConstraints& pin_constraints,
+                            const PinConstraintId& pin_constraint) {
+  /* Validate the file stream */
+  if (false == openfpga::valid_file_stream(fp)) {
+    return 2;
+  }
+
+  openfpga::write_tab_to_file(fp, 1);
+  fp << "<set_io";
+
+  if (false == pin_constraints.valid_pin_constraint_id(pin_constraint)) {
+    return 1;
+  }
+
+  write_xml_attribute(fp, "pin", generate_xml_port_name(pin_constraints.pin(pin_constraint)).c_str());
+  write_xml_attribute(fp, "net", pin_constraints.net(pin_constraint).c_str());
+
+  fp << "/>" << "\n";
+
+  return 0;
+}
+
+/********************************************************************
+ * A writer to output a repack pin constraint object to XML format
+ *
+ * Return 0 if successful
+ * Return 1 if there are more serious bugs in the architecture 
+ * Return 2 if fail when creating files
+ *******************************************************************/
+int write_xml_pin_constraints(const char* fname,
+                              const PinConstraints& pin_constraints) {
+
+  vtr::ScopedStartFinishTimer timer("Write Pin Constraints");
+
+  /* Create a file handler */
+  std::fstream fp;
+  /* Open the file stream */
+  fp.open(std::string(fname), std::fstream::out | std::fstream::trunc);
+
+  /* Validate the file stream */
+  openfpga::check_file_stream(fname, fp);
+  
+  /* Write the root node */
+  fp << "<pin_constraints>" << "\n";
+
+  int err_code = 0;
+
+  /* Write region by region */ 
+  for (const PinConstraintId& pin_constraint : pin_constraints.pin_constraints()) {
+    /* Write constraint by constraint */ 
+    err_code = write_xml_pin_constraint(fp, pin_constraints, pin_constraint);
+    if (0 != err_code) {
+      return err_code;
+    }
+  }
+
+  /* Finish writing the root node */
+  fp << "</pin_constraints>" << "\n";
+
+  /* Close the file stream */
+  fp.close();
+
+  return err_code;
+}
diff --git a/libopenfpga/libpcf/src/write_xml_pin_constraints.h b/libopenfpga/libpcf/src/write_xml_pin_constraints.h
new file mode 100644
index 000000000..c68b072b9
--- /dev/null
+++ b/libopenfpga/libpcf/src/write_xml_pin_constraints.h
@@ -0,0 +1,16 @@
+#ifndef WRITE_XML_PIN_CONSTRAINTS_H
+#define WRITE_XML_PIN_CONSTRAINTS_H
+
+/********************************************************************
+ * Include header files that are required by function declaration
+ *******************************************************************/
+#include <fstream>
+#include "pin_constraints.h"
+
+/********************************************************************
+ * Function declaration
+ *******************************************************************/
+int write_xml_pin_constraints(const char* fname,
+                              const PinConstraints& pin_constraints);
+
+#endif
diff --git a/libopenfpga/libpcf/test/test_xml_pcf.cpp b/libopenfpga/libpcf/test/test_xml_pcf.cpp
new file mode 100644
index 000000000..da91ddbcc
--- /dev/null
+++ b/libopenfpga/libpcf/test/test_xml_pcf.cpp
@@ -0,0 +1,33 @@
+/********************************************************************
+ * Unit test functions to validate the correctness of 
+ * 1. parser of data structures
+ * 2. writer of data structures
+ *******************************************************************/
+/* Headers from vtrutils */
+#include "vtr_assert.h"
+#include "vtr_log.h"
+
+/* Headers from fabric key */
+#include "read_xml_pin_constraints.h"
+#include "write_xml_pin_constraints.h"
+
+int main(int argc, const char** argv) {
+  /* Ensure we have only one or two argument */
+  VTR_ASSERT((2 == argc) || (3 == argc));
+
+  /* Parse the fabric key from an XML file */
+  PinConstraints pin_constraints = read_xml_pin_constraints(argv[1]);
+  VTR_LOG("Read the pin constraints from an XML file: %s.\n",
+          argv[1]);
+
+  /* Output pin constraints to an XML file
+   * This is optional only used when there is a second argument
+   */
+  if (3 <= argc) { 
+    write_xml_pin_constraints(argv[2], pin_constraints);
+    VTR_LOG("Echo the pin constraints to an XML file: %s.\n",
+            argv[2]);
+  }
+}
+
+