//
//  GTMStackTrace.m
//
//  Copyright 2007-2008 Google Inc.
//
//  Licensed under the Apache License, Version 2.0 (the "License"); you may not
//  use this file except in compliance with the License.  You may obtain a copy
//  of the License at
// 
//  http://www.apache.org/licenses/LICENSE-2.0
// 
//  Unless required by applicable law or agreed to in writing, software
//  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
//  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
//  License for the specific language governing permissions and limitations under
//  the License.
//

#include <stdlib.h>
#include <dlfcn.h>
#include <mach-o/nlist.h>
#include "GTMStackTrace.h"
#include "GTMObjC2Runtime.h"

// Structure representing a small portion of a stack, starting from the saved
// frame pointer, and continuing through the saved program counter.
struct GTMStackFrame {
  void *saved_fp;
#if defined (__ppc__) || defined(__ppc64__)
  void *padding;
#endif
  void *saved_pc;
};

struct GTMClassDescription {
  const char *class_name;
  Method *class_methods;
  unsigned int class_method_count;
  Method *instance_methods;
  unsigned int instance_method_count;
};

#pragma mark Private utility functions

static struct GTMClassDescription *GTMClassDescriptions(NSUInteger *total_count) {
  int class_count = objc_getClassList(nil, 0);
  struct GTMClassDescription *class_descs 
    = calloc(class_count, sizeof(struct GTMClassDescription));
  if (class_descs) {
    Class *classes = calloc(class_count, sizeof(Class));
    if (classes) {
      objc_getClassList(classes, class_count);
      for (int i = 0; i < class_count; ++i) {
        class_descs[i].class_methods 
          = class_copyMethodList(object_getClass(classes[i]), 
                                 &class_descs[i].class_method_count);
        class_descs[i].instance_methods 
          = class_copyMethodList(classes[i], 
                                 &class_descs[i].instance_method_count);
        class_descs[i].class_name = class_getName(classes[i]);
      }
      free(classes);
    } else {
      // COV_NF_START - Don't know how to force this in a unittest
      free(class_descs);
      class_count = 0;
      // COV_NF_END
    }
  }
  if (total_count) {
    *total_count = class_count;
  }
  return class_descs;
}

static void GTMFreeClassDescriptions(struct GTMClassDescription *class_descs, 
                                     NSUInteger count) {
  if (!class_descs) return;
  for (NSUInteger i = 0; i < count; ++i) {
    if (class_descs[i].instance_methods) {
      free(class_descs[i].instance_methods);
    }
    if (class_descs[i].class_methods) {
      free(class_descs[i].class_methods);
    }
  }
  free(class_descs);
}

#pragma mark Public functions

// __builtin_frame_address(0) is a gcc builtin that returns a pointer to the
// current frame pointer.  We then use the frame pointer to walk the stack
// picking off program counters and other saved frame pointers.  This works
// great on i386, but PPC requires a little more work because the PC (or link
// register) isn't always stored on the stack.
//   
NSUInteger GTMGetStackProgramCounters(void *outPcs[], NSUInteger count) {
  if (!outPcs || (count < 1)) return 0;
  
  struct GTMStackFrame *fp;
#if defined (__ppc__) || defined(__ppc64__)
  outPcs[0] = __builtin_return_address(0);
  fp = (struct GTMStackFrame *)__builtin_frame_address(1);
#elif defined (__i386__) || defined(__x86_64__)
  fp = (struct GTMStackFrame *)__builtin_frame_address(0);
#else
#error architecture not supported
#endif

  NSUInteger level = 0;
  while (level < count) {
    if (fp == NULL) {
      level--;
      break;
    }
    outPcs[level] = fp->saved_pc;
    level++;
    fp = (struct GTMStackFrame *)fp->saved_fp;
  }
  
  return level;
}

NSUInteger GTMGetStackAddressDescriptors(struct GTMAddressDescriptor outDescs[], 
                                         NSUInteger count) {
  if (count < 1 || !outDescs) return 0;
  
  void **pcs = calloc(count, sizeof(void*));
  if (!pcs) return 0;
  
  NSUInteger newSize = GTMGetStackProgramCounters(pcs, count);
  NSUInteger class_desc_count;
  
  // Get our obj-c class descriptions. This is expensive, so we do it once
  // at the top. We go through this because dladdr doesn't work with
  // obj methods.
  struct GTMClassDescription *class_descs 
    = GTMClassDescriptions(&class_desc_count);
  
  // Iterate through the stack.
  for (NSUInteger i = 0; i < newSize; ++i) {
    const char *class_name = NULL;
    Boolean is_class_method = FALSE;
    size_t smallest_diff = SIZE_MAX;
    struct GTMAddressDescriptor *currDesc = &outDescs[i];
    currDesc->address = pcs[i];
    Method best_method = NULL;
    // Iterate through all the classes we know of.
    for (NSUInteger j = 0; j < class_desc_count; ++j) {
      // First check the class methods.
      for (NSUInteger k = 0; k < class_descs[j].class_method_count; ++k) {
        IMP imp = method_getImplementation(class_descs[j].class_methods[k]);
        if (imp <= (IMP)currDesc->address) {
          size_t diff = (size_t)currDesc->address - (size_t)imp;
          if (diff < smallest_diff) {
            best_method = class_descs[j].class_methods[k];
            class_name = class_descs[j].class_name;
            is_class_method = TRUE;
            smallest_diff = diff;
          }
        }
      }
      // Then check the instance methods.
      for (NSUInteger k = 0; k < class_descs[j].instance_method_count; ++k) {
        IMP imp = method_getImplementation(class_descs[j].instance_methods[k]);
        if (imp <= (IMP)currDesc->address) {
          size_t diff = (size_t)currDesc->address - (size_t)imp;
          if (diff < smallest_diff) {
            best_method = class_descs[j].instance_methods[k];
            class_name = class_descs[j].class_name;
            is_class_method = TRUE;
            smallest_diff = diff;
          }
        }
      }
    }
    
    // If we have one, store it off.
    if (best_method) {
      currDesc->symbol = sel_getName(method_getName(best_method));
      currDesc->is_class_method = is_class_method;
      currDesc->class_name = class_name;
    }
    Dl_info info = { NULL, NULL, NULL, NULL };
    
    // Check to see if the one returned by dladdr is better.
    dladdr(currDesc->address, &info);
    if ((size_t)currDesc->address - (size_t)info.dli_saddr < smallest_diff) {
      currDesc->symbol = info.dli_sname;
      currDesc->is_class_method = FALSE;
      currDesc->class_name = NULL;
    }
    currDesc->filename = info.dli_fname;
  }
  GTMFreeClassDescriptions(class_descs, class_desc_count);
  free(pcs);
  return newSize;
}

NSString *GTMStackTrace(void) {
  // The maximum number of stack frames that we will walk.  We limit this so
  // that super-duper recursive functions (or bugs) don't send us for an
  // infinite loop.
  struct GTMAddressDescriptor descs[100];
  size_t depth = sizeof(descs) / sizeof(struct GTMAddressDescriptor);
  depth = GTMGetStackAddressDescriptors(descs, depth);
  
  NSMutableString *trace = [NSMutableString string];
  
  // Start at the second item so that GTMStackTrace and it's utility calls (of
  // which there is currently 1) is not included in the output.
  const size_t kTracesToStrip = 2;
  for (size_t i = kTracesToStrip; i < depth; i++) {
    if (descs[i].class_name) {
      [trace appendFormat:@"#%-2d 0x%08lx %s[%s %s]  (%s)\n",
       i - kTracesToStrip, descs[i].address, 
       (descs[i].is_class_method ? "+" : "-"),
       descs[i].class_name,
       (descs[i].symbol ? descs[i].symbol : "??"),
       (descs[i].filename  ? descs[i].filename  : "??")];
    } else {
      [trace appendFormat:@"#%-2d 0x%08lx %s()  (%s)\n",
       i - kTracesToStrip, descs[i].address,
       (descs[i].symbol ? descs[i].symbol : "??"),
       (descs[i].filename  ? descs[i].filename  : "??")];
    }
  }
  return trace;
}