NSDictionary+GRPC.m

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#import "NSDictionary+GRPC.h"

#include <grpc/support/alloc.h>

#pragma mark Category for binary metadata elements

@interface NSData (GRPCMetadata)
+ (instancetype)grpc_dataFromMetadataValue:(grpc_metadata *)metadata;

// Fill a metadata object with the binary value in this NSData and the given key.
- (void)grpc_initMetadata:(grpc_metadata *)metadata withKey:(NSString *)key;
@end

@implementation NSData (GRPCMetadata)
+ (instancetype)grpc_dataFromMetadataValue:(grpc_metadata *)metadata {
  // TODO(jcanizales): Should we use a non-copy constructor?
  return [self dataWithBytes:metadata->value length:metadata->value_length];
}

- (void)grpc_initMetadata:(grpc_metadata *)metadata withKey:(NSString *)key {
  // TODO(jcanizales): Encode Unicode chars as ASCII.
  metadata->key = [key stringByAppendingString:@"-bin"].UTF8String;
  metadata->value = self.bytes;
  metadata->value_length = self.length;
}
@end

#pragma mark Category for textual metadata elements

@interface NSString (GRPCMetadata)
+ (instancetype)grpc_stringFromMetadataValue:(grpc_metadata *)metadata;

// Fill a metadata object with the textual value in this NSString and the given key.
- (void)grpc_initMetadata:(grpc_metadata *)metadata withKey:(NSString *)key;
@end

@implementation NSString (GRPCMetadata)
+ (instancetype)grpc_stringFromMetadataValue:(grpc_metadata *)metadata {
  return [[self alloc] initWithBytes:metadata->value
                              length:metadata->value_length
                            encoding:NSASCIIStringEncoding];
}

- (void)grpc_initMetadata:(grpc_metadata *)metadata withKey:(NSString *)key {
  if ([key hasSuffix:@"-bin"]) {
    // Disallow this, as at best it will confuse the server. If the app really needs to send a
    // textual header with a name ending in "-bin", it can be done by removing the suffix and
    // encoding the NSString as a NSData object.
    //
    // Why raise an exception: In the most common case, the developer knows this won't happen in
    // their code, so the exception isn't triggered. In the rare cases when the developer can't
    // tell, it's easy enough to add a sanitizing filter before the header is set. There, the
    // developer can choose whether to drop such a header, or trim its name. Doing either ourselves,
    // silently, would be very unintuitive for the user.
    [NSException raise:NSInvalidArgumentException
                format:@"Metadata keys ending in '-bin' are reserved for NSData values."];
  }
  // TODO(jcanizales): Encode Unicode chars as ASCII.
  metadata->key = key.UTF8String;
  metadata->value = self.UTF8String;
  metadata->value_length = self.length;
}
@end

#pragma mark Category for metadata arrays

@implementation NSDictionary (GRPC)
+ (instancetype)grpc_dictionaryFromMetadata:(grpc_metadata *)entries count:(size_t)count {
  NSMutableDictionary *metadata = [NSMutableDictionary dictionaryWithCapacity:count];
  for (grpc_metadata *entry = entries; entry < entries + count; entry++) {
    // TODO(jcanizales): Verify in a C library test that it's converting header names to lower case
    // automatically.
    NSString *name = [NSString stringWithCString:entry->key encoding:NSASCIIStringEncoding];
    if (!name) {
      // log?
      continue;
    }
    id value;
    if ([name hasSuffix:@"-bin"]) {
      name = [name substringToIndex:name.length - 4];
      value = [NSData grpc_dataFromMetadataValue:entry];
    } else {
      value = [NSString grpc_stringFromMetadataValue:entry];
    }
    if (!metadata[name]) {
      metadata[name] = [NSMutableArray array];
    }
    [metadata[name] addObject:value];
  }
  return metadata;
}

- (grpc_metadata *)grpc_metadataArray {
  grpc_metadata *metadata = gpr_malloc([self count] * sizeof(grpc_metadata));
  int i = 0;
  for (id key in self) {
    id value = self[key];
    grpc_metadata *current = &metadata[i];
    if ([value respondsToSelector:@selector(grpc_initMetadata:withKey:)]) {
      [value grpc_initMetadata:current withKey:key];
    } else {
      [NSException raise:NSInvalidArgumentException
                  format:@"Metadata values must be NSString or NSData."];
    }
    i += 1;
  }
  return metadata;
}
@end