Merge pull request #6570 from dgquintas/better-compression-docs-and-names

Better compression docs and names
diff --git a/include/grpc/impl/codegen/compression_types.h b/include/grpc/impl/codegen/compression_types.h
index 0daccd9..8d2ec3b 100644
--- a/include/grpc/impl/codegen/compression_types.h
+++ b/include/grpc/impl/codegen/compression_types.h
@@ -41,10 +41,13 @@
 #endif
 
 /** To be used in channel arguments */
-#define GRPC_COMPRESSION_ALGORITHM_ARG "grpc.compression_algorithm"
-#define GRPC_COMPRESSION_ALGORITHM_STATE_ARG "grpc.compression_algorithm_state"
+#define GRPC_COMPRESSION_CHANNEL_DEFAULT_ALGORITHM \
+  "grpc.default_compression_algorithm"
+#define GRPC_COMPRESSION_CHANNEL_DEFAULT_LEVEL "grpc.default_compression_level"
+#define GRPC_COMPRESSION_CHANNEL_ENABLED_ALGORITHMS_BITSET \
+  "grpc.compression_enabled_algorithms_bitset"
 
-/* The various compression algorithms supported by GRPC */
+/* The various compression algorithms supported by gRPC */
 typedef enum {
   GRPC_COMPRESS_NONE = 0,
   GRPC_COMPRESS_DEFLATE,
@@ -53,6 +56,10 @@
   GRPC_COMPRESS_ALGORITHMS_COUNT
 } grpc_compression_algorithm;
 
+/** Compression levels allow a party with knowledge of its peer's accepted
+ * encodings to request compression in an abstract way. The level-algorithm
+ * mapping is performed internally and depends on the peer's supported
+ * compression algorithms. */
 typedef enum {
   GRPC_COMPRESS_LEVEL_NONE = 0,
   GRPC_COMPRESS_LEVEL_LOW,
@@ -62,8 +69,20 @@
 } grpc_compression_level;
 
 typedef struct grpc_compression_options {
-  uint32_t enabled_algorithms_bitset; /**< All algs are enabled by default */
-  grpc_compression_algorithm default_compression_algorithm; /**< for channel */
+  /** All algs are enabled by default. This option corresponds to the channel
+   * argument key behind \a GRPC_COMPRESSION_CHANNEL_ENABLED_ALGORITHMS_BITSET
+   */
+  uint32_t enabled_algorithms_bitset;
+
+  /** The default channel compression algorithm. It'll be used in the absence of
+   * call specific settings. This option corresponds to the channel argument key
+   * behind \a GRPC_COMPRESSION_CHANNEL_DEFAULT_ALGORITHM */
+  grpc_compression_algorithm default_compression_algorithm;
+
+  /** The default channel compression level. It'll be used in the absence of
+   * call specific settings. This option corresponds to the channel argument key
+   * behind \a GRPC_COMPRESSION_CHANNEL_DEFAULT_LEVEL */
+  grpc_compression_algorithm default_compression_level;
 } grpc_compression_options;
 
 #ifdef __cplusplus
diff --git a/src/core/lib/channel/channel_args.c b/src/core/lib/channel/channel_args.c
index 28d2d78..893cf07 100644
--- a/src/core/lib/channel/channel_args.c
+++ b/src/core/lib/channel/channel_args.c
@@ -170,7 +170,7 @@
   if (a == NULL) return 0;
   for (i = 0; i < a->num_args; ++i) {
     if (a->args[i].type == GRPC_ARG_INTEGER &&
-        !strcmp(GRPC_COMPRESSION_ALGORITHM_ARG, a->args[i].key)) {
+        !strcmp(GRPC_COMPRESSION_CHANNEL_DEFAULT_ALGORITHM, a->args[i].key)) {
       return (grpc_compression_algorithm)a->args[i].value.integer;
       break;
     }
@@ -182,7 +182,7 @@
     grpc_channel_args *a, grpc_compression_algorithm algorithm) {
   grpc_arg tmp;
   tmp.type = GRPC_ARG_INTEGER;
-  tmp.key = GRPC_COMPRESSION_ALGORITHM_ARG;
+  tmp.key = GRPC_COMPRESSION_CHANNEL_DEFAULT_ALGORITHM;
   tmp.value.integer = algorithm;
   return grpc_channel_args_copy_and_add(a, &tmp, 1);
 }
@@ -196,7 +196,8 @@
     size_t i;
     for (i = 0; i < a->num_args; ++i) {
       if (a->args[i].type == GRPC_ARG_INTEGER &&
-          !strcmp(GRPC_COMPRESSION_ALGORITHM_STATE_ARG, a->args[i].key)) {
+          !strcmp(GRPC_COMPRESSION_CHANNEL_ENABLED_ALGORITHMS_BITSET,
+                  a->args[i].key)) {
         *states_arg = &a->args[i].value.integer;
         return 1; /* GPR_TRUE */
       }
@@ -222,7 +223,7 @@
     /* create a new arg */
     grpc_arg tmp;
     tmp.type = GRPC_ARG_INTEGER;
-    tmp.key = GRPC_COMPRESSION_ALGORITHM_STATE_ARG;
+    tmp.key = GRPC_COMPRESSION_CHANNEL_ENABLED_ALGORITHMS_BITSET;
     /* all enabled by default */
     tmp.value.integer = (1u << GRPC_COMPRESS_ALGORITHMS_COUNT) - 1;
     if (state != 0) {
diff --git a/src/cpp/common/channel_arguments.cc b/src/cpp/common/channel_arguments.cc
index db3558f..f297ae8 100644
--- a/src/cpp/common/channel_arguments.cc
+++ b/src/cpp/common/channel_arguments.cc
@@ -85,7 +85,7 @@
 
 void ChannelArguments::SetCompressionAlgorithm(
     grpc_compression_algorithm algorithm) {
-  SetInt(GRPC_COMPRESSION_ALGORITHM_ARG, algorithm);
+  SetInt(GRPC_COMPRESSION_CHANNEL_DEFAULT_ALGORITHM, algorithm);
 }
 
 // Note: a second call to this will add in front the result of the first call.
diff --git a/src/cpp/server/server_builder.cc b/src/cpp/server/server_builder.cc
index 9658a56..61f0f6a 100644
--- a/src/cpp/server/server_builder.cc
+++ b/src/cpp/server/server_builder.cc
@@ -123,7 +123,7 @@
   if (max_message_size_ > 0) {
     args.SetInt(GRPC_ARG_MAX_MESSAGE_LENGTH, max_message_size_);
   }
-  args.SetInt(GRPC_COMPRESSION_ALGORITHM_STATE_ARG,
+  args.SetInt(GRPC_COMPRESSION_CHANNEL_ENABLED_ALGORITHMS_BITSET,
               compression_options_.enabled_algorithms_bitset);
   std::unique_ptr<Server> server(
       new Server(thread_pool.release(), true, max_message_size_, &args));
diff --git a/test/core/channel/channel_args_test.c b/test/core/channel/channel_args_test.c
index c7fc259..c2fc050 100644
--- a/test/core/channel/channel_args_test.c
+++ b/test/core/channel/channel_args_test.c
@@ -77,7 +77,8 @@
   ch_args =
       grpc_channel_args_set_compression_algorithm(NULL, GRPC_COMPRESS_GZIP);
   GPR_ASSERT(ch_args->num_args == 1);
-  GPR_ASSERT(strcmp(ch_args->args[0].key, GRPC_COMPRESSION_ALGORITHM_ARG) == 0);
+  GPR_ASSERT(strcmp(ch_args->args[0].key,
+                    GRPC_COMPRESSION_CHANNEL_DEFAULT_ALGORITHM) == 0);
   GPR_ASSERT(ch_args->args[0].type == GRPC_ARG_INTEGER);
 
   grpc_channel_args_destroy(ch_args);