Progress towards mdstr elimination

11 files changed, 156 insertions, 175 deletions

diff --git a/src/core/lib/compression/algorithm_metadata.h b/src/core/lib/compression/algorithm_metadata.h
index 7412054bfe..bc4963059c 100644
--- a/src/core/lib/compression/algorithm_metadata.h
+++ b/src/core/lib/compression/algorithm_metadata.h
@@ -38,7 +38,7 @@
 #include "src/core/lib/transport/metadata.h"
 
 /** Return compression algorithm based metadata value */
-grpc_slice grpc_compression_algorithm_mdstr(
+grpc_slice grpc_compression_algorithm_slice(
     grpc_compression_algorithm algorithm);
 
 /** Return compression algorithm based metadata element (grpc-encoding: xxx) */
@@ -47,7 +47,7 @@ grpc_mdelem *grpc_compression_encoding_mdelem(
 
 /** Find compression algorithm based on passed in mdstr - returns
  * GRPC_COMPRESS_ALGORITHM_COUNT on failure */
-grpc_compression_algorithm grpc_compression_algorithm_from_mdstr(
+grpc_compression_algorithm grpc_compression_algorithm_from_slice(
     grpc_slice str);
 
 #endif /* GRPC_CORE_LIB_COMPRESSION_ALGORITHM_METADATA_H */
diff --git a/src/core/lib/compression/compression.c b/src/core/lib/compression/compression.c
index aa3caf9fef..d73353f392 100644
--- a/src/core/lib/compression/compression.c
+++ b/src/core/lib/compression/compression.c
@@ -81,7 +81,7 @@ int grpc_compression_algorithm_name(grpc_compression_algorithm algorithm,
   return 0;
 }
 
-grpc_compression_algorithm grpc_compression_algorithm_from_mdstr(
+grpc_compression_algorithm grpc_compression_algorithm_from_slice(
     grpc_slice str) {
   if (grpc_slice_cmp(str, GRPC_MDSTR_IDENTITY) == 0) return GRPC_COMPRESS_NONE;
   if (grpc_slice_cmp(str, GRPC_MDSTR_DEFLATE) == 0)
@@ -90,7 +90,7 @@ grpc_compression_algorithm grpc_compression_algorithm_from_mdstr(
   return GRPC_COMPRESS_ALGORITHMS_COUNT;
 }
 
-grpc_slice grpc_compression_algorithm_mdstr(
+grpc_slice grpc_compression_algorithm_slice(
     grpc_compression_algorithm algorithm) {
   switch (algorithm) {
     case GRPC_COMPRESS_NONE:
diff --git a/src/core/lib/slice/slice_string_helpers.h b/src/core/lib/slice/slice_string_helpers.h
index c6f4e87c7f..4a4deec6e5 100644
--- a/src/core/lib/slice/slice_string_helpers.h
+++ b/src/core/lib/slice/slice_string_helpers.h
@@ -34,6 +34,7 @@
 #ifndef GRPC_CORE_LIB_SLICE_SLICE_STRING_HELPERS_H
 #define GRPC_CORE_LIB_SLICE_SLICE_STRING_HELPERS_H
 
+#include <stdbool.h>
 #include <stddef.h>
 
 #include <grpc/slice.h>
@@ -53,6 +54,8 @@ char *grpc_dump_slice(grpc_slice slice, uint32_t flags);
  * should be a properly initialized instance. */
 void grpc_slice_split(grpc_slice str, const char *sep, grpc_slice_buffer *dst);
 
+bool grpc_parse_slice_to_uint32(grpc_slice str, uint32_t *result);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/core/lib/surface/call.c b/src/core/lib/surface/call.c
index 525f7b663a..37548697fa 100644
--- a/src/core/lib/surface/call.c
+++ b/src/core/lib/surface/call.c
@@ -196,8 +196,7 @@ struct grpc_call {
   union {
     struct {
       grpc_status_code *status;
-      char **status_details;
-      size_t *status_details_capacity;
+      grpc_slice *status_details;
     } client;
     struct {
       int *cancelled;
@@ -383,7 +382,7 @@ static void get_final_status(grpc_call *call,
                              void *set_value_user_data) {
   int i;
   for (i = 0; i < STATUS_SOURCE_COUNT; i++) {
-    if (call->status[i].is_set) {
+    if (call->status[i].is_code_set) {
       set_value(call->status[i].code, set_value_user_data);
       return;
     }
@@ -411,8 +410,8 @@ static void destroy_call(grpc_exec_ctx *exec_ctx, void *call,
   }
   gpr_mu_destroy(&c->mu);
   for (i = 0; i < STATUS_SOURCE_COUNT; i++) {
-    if (c->status[i].details) {
-      GRPC_MDSTR_UNREF(exec_ctx, c->status[i].details);
+    if (c->status[i].is_details_set) {
+      grpc_slice_unref_internal(exec_ctx, c->status[i].details);
     }
   }
   for (ii = 0; ii < c->send_extra_metadata_count; ii++) {
@@ -438,18 +437,19 @@ static void destroy_call(grpc_exec_ctx *exec_ctx, void *call,
 
 static void set_status_code(grpc_call *call, status_source source,
                             uint32_t status) {
-  if (call->status[source].is_set) return;
+  if (call->status[source].is_code_set) return;
 
-  call->status[source].is_set = 1;
+  call->status[source].is_code_set = true;
   call->status[source].code = (grpc_status_code)status;
 }
 
 static void set_status_details(grpc_exec_ctx *exec_ctx, grpc_call *call,
                                status_source source, grpc_slice status) {
-  if (call->status[source].details != NULL) {
-    GRPC_MDSTR_UNREF(exec_ctx, status);
+  if (call->status[source].is_details_set) {
+    grpc_slice_unref_internal(exec_ctx, status);
   } else {
     call->status[source].details = status;
+    call->status[source].is_details_set = true;
   }
 }
 
@@ -459,7 +459,8 @@ static void set_status_from_error(grpc_exec_ctx *exec_ctx, grpc_call *call,
   const char *msg;
   grpc_error_get_status(error, &status, &msg);
   set_status_code(call, source, (uint32_t)status);
-  set_status_details(exec_ctx, call, source, grpc_mdstr_from_string(msg));
+  set_status_details(exec_ctx, call, source,
+                     grpc_slice_from_copied_string(msg));
 }
 
 static void set_incoming_compression_algorithm(
@@ -509,7 +510,7 @@ static void set_encodings_accepted_by_peer(grpc_exec_ctx *exec_ctx,
     return;
   }
 
-  accept_encoding_slice = mdel->value->slice;
+  accept_encoding_slice = mdel->value;
   grpc_slice_buffer_init(&accept_encoding_parts);
   grpc_slice_split(accept_encoding_slice, ",", &accept_encoding_parts);
 
@@ -518,15 +519,13 @@ static void set_encodings_accepted_by_peer(grpc_exec_ctx *exec_ctx,
   /* Always support no compression */
   GPR_BITSET(&call->encodings_accepted_by_peer, GRPC_COMPRESS_NONE);
   for (i = 0; i < accept_encoding_parts.count; i++) {
-    const grpc_slice *accept_encoding_entry_slice =
-        &accept_encoding_parts.slices[i];
-    if (grpc_compression_algorithm_parse(
-            (const char *)GRPC_SLICE_START_PTR(*accept_encoding_entry_slice),
-            GRPC_SLICE_LENGTH(*accept_encoding_entry_slice), &algorithm)) {
+    grpc_slice accept_encoding_entry_slice = accept_encoding_parts.slices[i];
+    if (grpc_compression_algorithm_parse(accept_encoding_entry_slice,
+                                         &algorithm)) {
       GPR_BITSET(&call->encodings_accepted_by_peer, algorithm);
     } else {
       char *accept_encoding_entry_str =
-          grpc_dump_slice(*accept_encoding_entry_slice, GPR_DUMP_ASCII);
+          grpc_dump_slice(accept_encoding_entry_slice, GPR_DUMP_ASCII);
       gpr_log(GPR_ERROR,
               "Invalid entry in accept encoding metadata: '%s'. Ignoring.",
               accept_encoding_entry_str);
@@ -549,21 +548,12 @@ uint32_t grpc_call_test_only_get_encodings_accepted_by_peer(grpc_call *call) {
   return encodings_accepted_by_peer;
 }
 
-static void get_final_details(grpc_call *call, char **out_details,
-                              size_t *out_details_capacity) {
+static void get_final_details(grpc_call *call, grpc_slice *out_details) {
   int i;
   for (i = 0; i < STATUS_SOURCE_COUNT; i++) {
-    if (call->status[i].is_set) {
-      if (call->status[i].details) {
-        grpc_slice details = call->status[i].details->slice;
-        size_t len = GRPC_SLICE_LENGTH(details);
-        if (len + 1 > *out_details_capacity) {
-          *out_details_capacity =
-              GPR_MAX(len + 1, *out_details_capacity * 3 / 2);
-          *out_details = gpr_realloc(*out_details, *out_details_capacity);
-        }
-        memcpy(*out_details, GRPC_SLICE_START_PTR(details), len);
-        (*out_details)[len] = 0;
+    if (call->status[i].is_code_set) {
+      if (call->status[i].is_details_set) {
+        *out_details = grpc_slice_ref(call->status[i].details);
       } else {
         goto no_details;
       }
@@ -572,11 +562,7 @@ static void get_final_details(grpc_call *call, char **out_details,
   }
 
 no_details:
-  if (0 == *out_details_capacity) {
-    *out_details_capacity = 8;
-    *out_details = gpr_malloc(*out_details_capacity);
-  }
-  **out_details = 0;
+  *out_details = grpc_empty_slice();
 }
 
 static grpc_linked_mdelem *linked_from_md(grpc_metadata *md) {
@@ -605,19 +591,17 @@ static int prepare_application_metadata(
         get_md_elem(metadata, additional_metadata, i, count);
     grpc_linked_mdelem *l = (grpc_linked_mdelem *)&md->internal_data;
     GPR_ASSERT(sizeof(grpc_linked_mdelem) == sizeof(md->internal_data));
-    l->md = grpc_mdelem_from_string_and_buffer(
-        exec_ctx, md->key, (const uint8_t *)md->value, md->value_length);
-    if (!grpc_header_key_is_legal(grpc_mdstr_as_c_string(l->md->key),
-                                  GRPC_MDSTR_LENGTH(l->md->key))) {
-      gpr_log(GPR_ERROR, "attempt to send invalid metadata key: %s",
-              grpc_mdstr_as_c_string(l->md->key));
+    l->md = grpc_mdelem_from_slices(exec_ctx, md->key, md->value);
+    if (!grpc_header_key_slice_is_legal(l->md->key)) {
+      char *str = grpc_dump_slice(md->key, GPR_DUMP_ASCII);
+      gpr_log(GPR_ERROR, "attempt to send invalid metadata key: %s", str);
+      gpr_free(str);
       break;
-    } else if (!grpc_is_binary_header(grpc_mdstr_as_c_string(l->md->key),
-                                      GRPC_MDSTR_LENGTH(l->md->key)) &&
-               !grpc_header_nonbin_value_is_legal(
-                   grpc_mdstr_as_c_string(l->md->value),
-                   GRPC_MDSTR_LENGTH(l->md->value))) {
-      gpr_log(GPR_ERROR, "attempt to send invalid metadata value");
+    } else if (!grpc_slice_is_binary_header(l->md->key) &&
+               !grpc_header_nonbin_value_slice_is_legal(l->md->value)) {
+      char *str = grpc_dump_slice(md->value, GPR_DUMP_HEX | GPR_DUMP_ASCII);
+      gpr_log(GPR_ERROR, "attempt to send invalid metadata value: %s", str);
+      gpr_free(str);
       break;
     }
   }
@@ -902,9 +886,7 @@ static uint32_t decode_status(grpc_mdelem *md) {
   if (user_data != NULL) {
     status = ((uint32_t)(intptr_t)user_data) - STATUS_OFFSET;
   } else {
-    if (!gpr_parse_bytes_to_uint32(grpc_mdstr_as_c_string(md->value),
-                                   GRPC_SLICE_LENGTH(md->value->slice),
-                                   &status)) {
+    if (!grpc_parse_slice_to_uint32(md->value, &status)) {
       status = GRPC_STATUS_UNKNOWN; /* could not parse status code */
     }
     grpc_mdelem_set_user_data(md, destroy_status,
@@ -915,13 +897,14 @@ static uint32_t decode_status(grpc_mdelem *md) {
 
 static grpc_compression_algorithm decode_compression(grpc_mdelem *md) {
   grpc_compression_algorithm algorithm =
-      grpc_compression_algorithm_from_mdstr(md->value);
+      grpc_compression_algorithm_from_slice(md->value);
   if (algorithm == GRPC_COMPRESS_ALGORITHMS_COUNT) {
-    const char *md_c_str = grpc_mdstr_as_c_string(md->value);
+    char *md_c_str = grpc_dump_slice(md->value, GPR_DUMP_ASCII);
     gpr_log(GPR_ERROR,
             "Invalid incoming compression algorithm: '%s'. Interpreting "
             "incoming data as uncompressed.",
             md_c_str);
+    gpr_free(md_c_str);
     return GRPC_COMPRESS_NONE;
   }
   return algorithm;
@@ -929,15 +912,15 @@ static grpc_compression_algorithm decode_compression(grpc_mdelem *md) {
 
 static grpc_mdelem *recv_common_filter(grpc_exec_ctx *exec_ctx, grpc_call *call,
                                        grpc_mdelem *elem) {
-  if (elem->key == GRPC_MDSTR_GRPC_STATUS) {
+  if (grpc_slice_cmp(elem->key, GRPC_MDSTR_GRPC_STATUS) == 0) {
     GPR_TIMER_BEGIN("status", 0);
     set_status_code(call, STATUS_FROM_WIRE, decode_status(elem));
     GPR_TIMER_END("status", 0);
     return NULL;
-  } else if (elem->key == GRPC_MDSTR_GRPC_MESSAGE) {
+  } else if (grpc_slice_cmp(elem->key, GRPC_MDSTR_GRPC_MESSAGE) == 0) {
     GPR_TIMER_BEGIN("status-details", 0);
     set_status_details(exec_ctx, call, STATUS_FROM_WIRE,
-                       GRPC_MDSTR_REF(elem->value));
+                       grpc_slice_ref_internal(elem->value));
     GPR_TIMER_END("status-details", 0);
     return NULL;
   }
@@ -956,9 +939,8 @@ static grpc_mdelem *publish_app_metadata(grpc_call *call, grpc_mdelem *elem,
         gpr_realloc(dest->metadata, sizeof(grpc_metadata) * dest->capacity);
   }
   mdusr = &dest->metadata[dest->count++];
-  mdusr->key = grpc_mdstr_as_c_string(elem->key);
-  mdusr->value = grpc_mdstr_as_c_string(elem->value);
-  mdusr->value_length = GRPC_SLICE_LENGTH(elem->value->slice);
+  mdusr->key = grpc_slice_ref(elem->key);
+  mdusr->value = grpc_slice_ref(elem->value);
   GPR_TIMER_END("publish_app_metadata", 0);
   return elem;
 }
@@ -973,12 +955,12 @@ static grpc_mdelem *recv_initial_filter(void *args, grpc_mdelem *elem) {
   elem = recv_common_filter(a->exec_ctx, a->call, elem);
   if (elem == NULL) {
     return NULL;
-  } else if (elem->key == GRPC_MDSTR_GRPC_ENCODING) {
+  } else if (grpc_slice_cmp(elem->key, GRPC_MDSTR_GRPC_ENCODING) == 0) {
     GPR_TIMER_BEGIN("incoming_compression_algorithm", 0);
     set_incoming_compression_algorithm(a->call, decode_compression(elem));
     GPR_TIMER_END("incoming_compression_algorithm", 0);
     return NULL;
-  } else if (elem->key == GRPC_MDSTR_GRPC_ACCEPT_ENCODING) {
+  } else if (grpc_slice_cmp(elem->key, GRPC_MDSTR_GRPC_ACCEPT_ENCODING) == 0) {
     GPR_TIMER_BEGIN("encodings_accepted_by_peer", 0);
     set_encodings_accepted_by_peer(a->exec_ctx, a->call, elem);
     GPR_TIMER_END("encodings_accepted_by_peer", 0);
@@ -1328,8 +1310,7 @@ static void finish_batch(grpc_exec_ctx *exec_ctx, void *bctlp,
     if (call->is_client) {
       get_final_status(call, set_status_value_directly,
                        call->final_op.client.status);
-      get_final_details(call, call->final_op.client.status_details,
-                        call->final_op.client.status_details_capacity);
+      get_final_details(call, call->final_op.client.status_details);
     } else {
       get_final_status(call, set_cancelled_value,
                        call->final_op.server.cancelled);
@@ -1427,13 +1408,10 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
           const grpc_compression_algorithm calgo =
               compression_algorithm_for_level_locked(
                   call, effective_compression_level);
-          char *calgo_name = NULL;
-          grpc_compression_algorithm_name(calgo, &calgo_name);
           // the following will be picked up by the compress filter and used as
           // the call's compression algorithm.
-          compression_md.key = GRPC_COMPRESSION_REQUEST_ALGORITHM_MD_KEY;
-          compression_md.value = calgo_name;
-          compression_md.value_length = strlen(calgo_name);
+          compression_md.key = GRPC_MDSTR_GRPC_INTERNAL_ENCODING_REQUEST;
+          compression_md.value = grpc_compression_algorithm_slice(calgo);
           additional_metadata_count++;
         }
 
@@ -1527,14 +1505,14 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
         call->send_extra_metadata[0].md = grpc_channel_get_reffed_status_elem(
             exec_ctx, call->channel, op->data.send_status_from_server.status);
         if (op->data.send_status_from_server.status_details != NULL) {
-          call->send_extra_metadata[1].md = grpc_mdelem_from_metadata_strings(
+          call->send_extra_metadata[1].md = grpc_mdelem_from_slices(
               exec_ctx, GRPC_MDSTR_GRPC_MESSAGE,
-              grpc_mdstr_from_string(
-                  op->data.send_status_from_server.status_details));
+              grpc_slice_ref_internal(
+                  *op->data.send_status_from_server.status_details));
           call->send_extra_metadata_count++;
           set_status_details(
               exec_ctx, call, STATUS_FROM_API_OVERRIDE,
-              GRPC_MDSTR_REF(call->send_extra_metadata[1].md->value));
+              grpc_slice_ref_internal(call->send_extra_metadata[1].md->value));
         }
         if (op->data.send_status_from_server.status != GRPC_STATUS_OK) {
           set_status_code(call, STATUS_FROM_API_OVERRIDE,
@@ -1611,8 +1589,6 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
         call->final_op.client.status = op->data.recv_status_on_client.status;
         call->final_op.client.status_details =
             op->data.recv_status_on_client.status_details;
-        call->final_op.client.status_details_capacity =
-            op->data.recv_status_on_client.status_details_capacity;
         bctl->recv_final_op = 1;
         stream_op->recv_trailing_metadata =
             &call->metadata_batch[1 /* is_receiving */][1 /* is_trailing */];
diff --git a/src/core/lib/surface/call_details.c b/src/core/lib/surface/call_details.c
index fe73da3f55..5efa3b0141 100644
--- a/src/core/lib/surface/call_details.c
+++ b/src/core/lib/surface/call_details.c
@@ -41,10 +41,12 @@
 void grpc_call_details_init(grpc_call_details* cd) {
   GRPC_API_TRACE("grpc_call_details_init(cd=%p)", 1, (cd));
   memset(cd, 0, sizeof(*cd));
+  cd->method = grpc_empty_slice();
+  cd->host = grpc_empty_slice();
 }
 
 void grpc_call_details_destroy(grpc_call_details* cd) {
   GRPC_API_TRACE("grpc_call_details_destroy(cd=%p)", 1, (cd));
-  gpr_free(cd->method);
-  gpr_free(cd->host);
+  grpc_slice_unref(cd->method);
+  grpc_slice_unref(cd->host);
 }
diff --git a/src/core/lib/surface/call_log_batch.c b/src/core/lib/surface/call_log_batch.c
index 31c074f15d..8f6438bc3b 100644
--- a/src/core/lib/surface/call_log_batch.c
+++ b/src/core/lib/surface/call_log_batch.c
@@ -35,17 +35,18 @@
 
 #include <grpc/support/alloc.h>
 #include <grpc/support/string_util.h>
+#include "src/core/lib/slice/slice_string_helpers.h"
 #include "src/core/lib/support/string.h"
 
 static void add_metadata(gpr_strvec *b, const grpc_metadata *md, size_t count) {
   size_t i;
   for (i = 0; i < count; i++) {
     gpr_strvec_add(b, gpr_strdup("\nkey="));
-    gpr_strvec_add(b, gpr_strdup(md[i].key));
+    gpr_strvec_add(b, grpc_dump_slice(md[i].key, GPR_DUMP_ASCII));
 
     gpr_strvec_add(b, gpr_strdup(" value="));
-    gpr_strvec_add(b, gpr_dump(md[i].value, md[i].value_length,
-                               GPR_DUMP_HEX | GPR_DUMP_ASCII));
+    gpr_strvec_add(b,
+                   grpc_dump_slice(md[i].value, GPR_DUMP_HEX | GPR_DUMP_ASCII));
   }
 }
 
@@ -70,10 +71,16 @@ char *grpc_op_string(const grpc_op *op) {
       gpr_strvec_add(&b, gpr_strdup("SEND_CLOSE_FROM_CLIENT"));
       break;
     case GRPC_OP_SEND_STATUS_FROM_SERVER:
-      gpr_asprintf(&tmp, "SEND_STATUS_FROM_SERVER status=%d details=%s",
-                   op->data.send_status_from_server.status,
-                   op->data.send_status_from_server.status_details);
+      gpr_asprintf(&tmp, "SEND_STATUS_FROM_SERVER status=%d details=",
+                   op->data.send_status_from_server.status);
       gpr_strvec_add(&b, tmp);
+      if (op->data.send_status_from_server.status_details != NULL) {
+        gpr_strvec_add(&b, grpc_dump_slice(
+                               *op->data.send_status_from_server.status_details,
+                               GPR_DUMP_ASCII));
+      } else {
+        gpr_strvec_add(&b, gpr_strdup("(null)"));
+      }
       add_metadata(&b, op->data.send_status_from_server.trailing_metadata,
                    op->data.send_status_from_server.trailing_metadata_count);
       break;
diff --git a/src/core/lib/surface/channel.c b/src/core/lib/surface/channel.c
index 7e87f05531..986142a692 100644
--- a/src/core/lib/surface/channel.c
+++ b/src/core/lib/surface/channel.c
@@ -123,8 +123,9 @@ grpc_channel *grpc_channel_create(grpc_exec_ctx *exec_ctx, const char *target,
             /* setting this takes precedence over anything else */
             GRPC_MDELEM_UNREF(exec_ctx, channel->default_authority);
           }
-          channel->default_authority = grpc_mdelem_from_strings(
-              exec_ctx, ":authority", args->args[i].value.string);
+          channel->default_authority = grpc_mdelem_from_slices(
+              exec_ctx, GRPC_MDSTR_AUTHORITY,
+              grpc_slice_from_copied_string(args->args[i].value.string));
         }
       } else if (0 ==
                  strcmp(args->args[i].key, GRPC_SSL_TARGET_NAME_OVERRIDE_ARG)) {
@@ -138,8 +139,9 @@ grpc_channel *grpc_channel_create(grpc_exec_ctx *exec_ctx, const char *target,
                     "%s ignored: default host already set some other way",
                     GRPC_SSL_TARGET_NAME_OVERRIDE_ARG);
           } else {
-            channel->default_authority = grpc_mdelem_from_strings(
-                exec_ctx, ":authority", args->args[i].value.string);
+            channel->default_authority = grpc_mdelem_from_slices(
+                exec_ctx, GRPC_MDSTR_AUTHORITY,
+                grpc_slice_from_copied_string(args->args[i].value.string));
           }
         }
       } else if (0 == strcmp(args->args[i].key,
@@ -224,27 +226,17 @@ grpc_call *grpc_channel_create_call(grpc_channel *channel,
                                     grpc_call *parent_call,
                                     uint32_t propagation_mask,
                                     grpc_completion_queue *cq,
-                                    const char *method, const char *host,
+                                    grpc_slice method, const grpc_slice *host,
                                     gpr_timespec deadline, void *reserved) {
-  GRPC_API_TRACE(
-      "grpc_channel_create_call("
-      "channel=%p, parent_call=%p, propagation_mask=%x, cq=%p, method=%s, "
-      "host=%s, "
-      "deadline=gpr_timespec { tv_sec: %" PRId64
-      ", tv_nsec: %d, clock_type: %d }, "
-      "reserved=%p)",
-      10,
-      (channel, parent_call, (unsigned)propagation_mask, cq, method, host,
-       deadline.tv_sec, deadline.tv_nsec, (int)deadline.clock_type, reserved));
   GPR_ASSERT(!reserved);
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   grpc_call *call = grpc_channel_create_call_internal(
       &exec_ctx, channel, parent_call, propagation_mask, cq, NULL,
-      grpc_mdelem_from_metadata_strings(&exec_ctx, GRPC_MDSTR_PATH,
-                                        grpc_mdstr_from_string(method)),
-      host ? grpc_mdelem_from_metadata_strings(&exec_ctx, GRPC_MDSTR_AUTHORITY,
-                                               grpc_mdstr_from_string(host))
-           : NULL,
+      grpc_mdelem_from_slices(&exec_ctx, GRPC_MDSTR_PATH,
+                              grpc_slice_ref(method)),
+      host != NULL ? grpc_mdelem_from_slices(&exec_ctx, GRPC_MDSTR_AUTHORITY,
+                                             grpc_slice_ref(*host))
+                   : NULL,
       deadline);
   grpc_exec_ctx_finish(&exec_ctx);
   return call;
@@ -252,17 +244,16 @@ grpc_call *grpc_channel_create_call(grpc_channel *channel,
 
 grpc_call *grpc_channel_create_pollset_set_call(
     grpc_exec_ctx *exec_ctx, grpc_channel *channel, grpc_call *parent_call,
-    uint32_t propagation_mask, grpc_pollset_set *pollset_set,
-    const char *method, const char *host, gpr_timespec deadline,
-    void *reserved) {
+    uint32_t propagation_mask, grpc_pollset_set *pollset_set, grpc_slice method,
+    const grpc_slice *host, gpr_timespec deadline, void *reserved) {
   GPR_ASSERT(!reserved);
   return grpc_channel_create_call_internal(
       exec_ctx, channel, parent_call, propagation_mask, NULL, pollset_set,
-      grpc_mdelem_from_metadata_strings(exec_ctx, GRPC_MDSTR_PATH,
-                                        grpc_mdstr_from_string(method)),
-      host ? grpc_mdelem_from_metadata_strings(exec_ctx, GRPC_MDSTR_AUTHORITY,
-                                               grpc_mdstr_from_string(host))
-           : NULL,
+      grpc_mdelem_from_slices(exec_ctx, GRPC_MDSTR_PATH,
+                              grpc_slice_ref(method)),
+      host != NULL ? grpc_mdelem_from_slices(exec_ctx, GRPC_MDSTR_AUTHORITY,
+                                             grpc_slice_ref(*host))
+                   : NULL,
       deadline);
 }
 
@@ -274,11 +265,14 @@ void *grpc_channel_register_call(grpc_channel *channel, const char *method,
       4, (channel, method, host, reserved));
   GPR_ASSERT(!reserved);
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  rc->path = grpc_mdelem_from_metadata_strings(&exec_ctx, GRPC_MDSTR_PATH,
-                                               grpc_mdstr_from_string(method));
+
+  rc->path = grpc_mdelem_from_slices(
+      &exec_ctx, GRPC_MDSTR_PATH,
+      grpc_slice_intern(grpc_slice_from_copied_string(method)));
   rc->authority =
-      host ? grpc_mdelem_from_metadata_strings(&exec_ctx, GRPC_MDSTR_AUTHORITY,
-                                               grpc_mdstr_from_string(host))
+      host ? grpc_mdelem_from_slices(
+                 &exec_ctx, GRPC_MDSTR_AUTHORITY,
+                 grpc_slice_intern(grpc_slice_from_copied_string(host)))
            : NULL;
   gpr_mu_lock(&channel->registered_call_mu);
   rc->next = channel->registered_calls;
@@ -385,6 +379,6 @@ grpc_mdelem *grpc_channel_get_reffed_status_elem(grpc_exec_ctx *exec_ctx,
       return GRPC_MDELEM_GRPC_STATUS_2;
   }
   gpr_ltoa(i, tmp);
-  return grpc_mdelem_from_metadata_strings(exec_ctx, GRPC_MDSTR_GRPC_STATUS,
-                                           grpc_mdstr_from_string(tmp));
+  return grpc_mdelem_from_slices(exec_ctx, GRPC_MDSTR_GRPC_STATUS,
+                                 grpc_slice_from_copied_string(tmp));
 }
diff --git a/src/core/lib/surface/channel.h b/src/core/lib/surface/channel.h
index 2ebadb7a15..cbe48cd6a0 100644
--- a/src/core/lib/surface/channel.h
+++ b/src/core/lib/surface/channel.h
@@ -52,9 +52,8 @@ grpc_channel *grpc_channel_create(grpc_exec_ctx *exec_ctx, const char *target,
     value of \a propagation_mask (see propagation_bits.h for possible values) */
 grpc_call *grpc_channel_create_pollset_set_call(
     grpc_exec_ctx *exec_ctx, grpc_channel *channel, grpc_call *parent_call,
-    uint32_t propagation_mask, grpc_pollset_set *pollset_set,
-    const char *method, const char *host, gpr_timespec deadline,
-    void *reserved);
+    uint32_t propagation_mask, grpc_pollset_set *pollset_set, grpc_slice method,
+    const grpc_slice *host, gpr_timespec deadline, void *reserved);
 
 /** Get a (borrowed) pointer to this channels underlying channel stack */
 grpc_channel_stack *grpc_channel_get_channel_stack(grpc_channel *channel);
diff --git a/src/core/lib/surface/lame_client.c b/src/core/lib/surface/lame_client.c
index d606f70c2f..a43969be57 100644
--- a/src/core/lib/surface/lame_client.c
+++ b/src/core/lib/surface/lame_client.c
@@ -44,6 +44,7 @@
 #include "src/core/lib/surface/api_trace.h"
 #include "src/core/lib/surface/call.h"
 #include "src/core/lib/surface/channel.h"
+#include "src/core/lib/transport/static_metadata.h"
 
 typedef struct {
   grpc_linked_mdelem status;
@@ -61,9 +62,11 @@ static void fill_metadata(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
   channel_data *chand = elem->channel_data;
   char tmp[GPR_LTOA_MIN_BUFSIZE];
   gpr_ltoa(chand->error_code, tmp);
-  calld->status.md = grpc_mdelem_from_strings(exec_ctx, "grpc-status", tmp);
-  calld->details.md =
-      grpc_mdelem_from_strings(exec_ctx, "grpc-message", chand->error_message);
+  calld->status.md = grpc_mdelem_from_slices(
+      exec_ctx, GRPC_MDSTR_GRPC_STATUS, grpc_slice_from_copied_string(tmp));
+  calld->details.md = grpc_mdelem_from_slices(
+      exec_ctx, GRPC_MDSTR_GRPC_MESSAGE,
+      grpc_slice_from_copied_string(chand->error_message));
   calld->status.prev = calld->details.next = NULL;
   calld->status.next = &calld->details;
   calld->details.prev = &calld->status;
diff --git a/src/core/lib/surface/server.c b/src/core/lib/surface/server.c
index 8f0cfbbc17..74411f3aab 100644
--- a/src/core/lib/surface/server.c
+++ b/src/core/lib/surface/server.c
@@ -98,6 +98,7 @@ typedef struct requested_call {
 typedef struct channel_registered_method {
   registered_method *server_registered_method;
   uint32_t flags;
+  bool has_host;
   grpc_slice method;
   grpc_slice host;
 } channel_registered_method;
@@ -144,6 +145,8 @@ struct call_data {
   /** the current state of a call - see call_state */
   call_state state;
 
+  bool path_set;
+  bool host_set;
   grpc_slice path;
   grpc_slice host;
   gpr_timespec deadline;
@@ -459,17 +462,6 @@ static void destroy_channel(grpc_exec_ctx *exec_ctx, channel_data *chand,
                        op);
 }
 
-static void cpstr(char **dest, size_t *capacity, grpc_slice value) {
-  grpc_slice slice = value->slice;
-  size_t len = GRPC_SLICE_LENGTH(slice);
-
-  if (len + 1 > *capacity) {
-    *capacity = GPR_MAX(len + 1, *capacity * 2);
-    *dest = gpr_realloc(*dest, *capacity);
-  }
-  memcpy(*dest, grpc_mdstr_as_c_string(value), len + 1);
-}
-
 static void done_request_event(grpc_exec_ctx *exec_ctx, void *req,
                                grpc_cq_completion *c) {
   requested_call *rc = req;
@@ -498,12 +490,10 @@ static void publish_call(grpc_exec_ctx *exec_ctx, grpc_server *server,
   GPR_SWAP(grpc_metadata_array, *rc->initial_metadata, calld->initial_metadata);
   switch (rc->type) {
     case BATCH_CALL:
-      GPR_ASSERT(calld->host != NULL);
-      GPR_ASSERT(calld->path != NULL);
-      cpstr(&rc->data.batch.details->host,
-            &rc->data.batch.details->host_capacity, calld->host);
-      cpstr(&rc->data.batch.details->method,
-            &rc->data.batch.details->method_capacity, calld->path);
+      GPR_ASSERT(calld->host_set);
+      GPR_ASSERT(calld->path_set);
+      rc->data.batch.details->host = grpc_slice_ref_internal(calld->host);
+      rc->data.batch.details->method = grpc_slice_ref_internal(calld->path);
       rc->data.batch.details->deadline = calld->deadline;
       rc->data.batch.details->flags =
           (calld->recv_idempotent_request
@@ -623,35 +613,39 @@ static void start_new_rpc(grpc_exec_ctx *exec_ctx, grpc_call_element *elem) {
   uint32_t hash;
   channel_registered_method *rm;
 
-  if (chand->registered_methods && calld->path && calld->host) {
+  if (chand->registered_methods && calld->path_set && calld->host_set) {
     /* TODO(ctiller): unify these two searches */
     /* check for an exact match with host */
-    hash = GRPC_MDSTR_KV_HASH(calld->host->hash, calld->path->hash);
+    hash = GRPC_MDSTR_KV_HASH(grpc_slice_hash(calld->host),
+                              grpc_slice_hash(calld->path));
     for (i = 0; i <= chand->registered_method_max_probes; i++) {
       rm = &chand->registered_methods[(hash + i) %
                                       chand->registered_method_slots];
       if (!rm) break;
-      if (rm->host != calld->host) continue;
-      if (rm->method != calld->path) continue;
+      if (!rm->has_host) continue;
+      if (grpc_slice_cmp(rm->host, calld->host) != 0) continue;
+      if (grpc_slice_cmp(rm->method, calld->path) != 0) continue;
       if ((rm->flags & GRPC_INITIAL_METADATA_IDEMPOTENT_REQUEST) &&
-          !calld->recv_idempotent_request)
+          !calld->recv_idempotent_request) {
         continue;
+      }
       finish_start_new_rpc(exec_ctx, server, elem,
                            &rm->server_registered_method->request_matcher,
                            rm->server_registered_method->payload_handling);
       return;
     }
     /* check for a wildcard method definition (no host set) */
-    hash = GRPC_MDSTR_KV_HASH(0, calld->path->hash);
+    hash = GRPC_MDSTR_KV_HASH(0, grpc_slice_hash(calld->path));
     for (i = 0; i <= chand->registered_method_max_probes; i++) {
       rm = &chand->registered_methods[(hash + i) %
                                       chand->registered_method_slots];
       if (!rm) break;
-      if (rm->host != NULL) continue;
-      if (rm->method != calld->path) continue;
+      if (rm->has_host) continue;
+      if (grpc_slice_cmp(rm->method, calld->path) != 0) continue;
       if ((rm->flags & GRPC_INITIAL_METADATA_IDEMPOTENT_REQUEST) &&
-          !calld->recv_idempotent_request)
+          !calld->recv_idempotent_request) {
         continue;
+      }
       finish_start_new_rpc(exec_ctx, server, elem,
                            &rm->server_registered_method->request_matcher,
                            rm->server_registered_method->payload_handling);
@@ -743,14 +737,14 @@ static void maybe_finish_shutdown(grpc_exec_ctx *exec_ctx,
 static grpc_mdelem *server_filter(void *user_data, grpc_mdelem *md) {
   grpc_call_element *elem = user_data;
   call_data *calld = elem->call_data;
-  if (md->key == GRPC_MDSTR_PATH) {
-    if (calld->path == NULL) {
-      calld->path = GRPC_MDSTR_REF(md->value);
+  if (grpc_slice_cmp(md->key, GRPC_MDSTR_PATH) == 0) {
+    if (!calld->path_set) {
+      calld->path = grpc_slice_ref(md->value);
     }
     return NULL;
-  } else if (md->key == GRPC_MDSTR_AUTHORITY) {
-    if (calld->host == NULL) {
-      calld->host = GRPC_MDSTR_REF(md->value);
+  } else if (grpc_slice_cmp(md->key, GRPC_MDSTR_AUTHORITY) == 0) {
+    if (!calld->host_set) {
+      calld->host = grpc_slice_ref(md->value);
     }
     return NULL;
   }
@@ -770,7 +764,7 @@ static void server_on_recv_initial_metadata(grpc_exec_ctx *exec_ctx, void *ptr,
   if (0 != gpr_time_cmp(op_deadline, gpr_inf_future(op_deadline.clock_type))) {
     calld->deadline = op_deadline;
   }
-  if (calld->host && calld->path) {
+  if (calld->host_set && calld->path_set) {
     /* do nothing */
   } else {
     GRPC_ERROR_UNREF(error);
@@ -902,11 +896,11 @@ static void destroy_call_elem(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
 
   GPR_ASSERT(calld->state != PENDING);
 
-  if (calld->host) {
-    GRPC_MDSTR_UNREF(exec_ctx, calld->host);
+  if (calld->host_set) {
+    grpc_slice_unref_internal(exec_ctx, calld->host);
   }
-  if (calld->path) {
-    GRPC_MDSTR_UNREF(exec_ctx, calld->path);
+  if (calld->path_set) {
+    grpc_slice_unref_internal(exec_ctx, calld->path);
   }
   grpc_metadata_array_destroy(&calld->initial_metadata);
 
@@ -936,11 +930,9 @@ static void destroy_channel_elem(grpc_exec_ctx *exec_ctx,
   channel_data *chand = elem->channel_data;
   if (chand->registered_methods) {
     for (i = 0; i < chand->registered_method_slots; i++) {
-      if (chand->registered_methods[i].method) {
-        GRPC_MDSTR_UNREF(exec_ctx, chand->registered_methods[i].method);
-      }
-      if (chand->registered_methods[i].host) {
-        GRPC_MDSTR_UNREF(exec_ctx, chand->registered_methods[i].host);
+      grpc_slice_unref_internal(exec_ctx, chand->registered_methods[i].method);
+      if (chand->registered_methods[i].has_host) {
+        grpc_slice_unref_internal(exec_ctx, chand->registered_methods[i].host);
       }
     }
     gpr_free(chand->registered_methods);
@@ -1136,8 +1128,6 @@ void grpc_server_setup_transport(grpc_exec_ctx *exec_ctx, grpc_server *s,
   channel_registered_method *crm;
   grpc_channel *channel;
   channel_data *chand;
-  grpc_slice host;
-  grpc_slice method;
   uint32_t hash;
   size_t slots;
   uint32_t probes;
@@ -1176,9 +1166,18 @@ void grpc_server_setup_transport(grpc_exec_ctx *exec_ctx, grpc_server *s,
     chand->registered_methods = gpr_malloc(alloc);
     memset(chand->registered_methods, 0, alloc);
     for (rm = s->registered_methods; rm; rm = rm->next) {
-      host = rm->host ? grpc_mdstr_from_string(rm->host) : NULL;
-      method = grpc_mdstr_from_string(rm->method);
-      hash = GRPC_MDSTR_KV_HASH(host ? host->hash : 0, method->hash);
+      grpc_slice host;
+      bool has_host;
+      grpc_slice method;
+      if (rm->host != NULL) {
+        host = grpc_slice_intern(grpc_slice_from_copied_string(rm->host));
+        has_host = true;
+      } else {
+        has_host = false;
+      }
+      method = grpc_slice_intern(grpc_slice_from_copied_string(rm->method));
+      hash = GRPC_MDSTR_KV_HASH(has_host ? grpc_slice_hash(host) : 0,
+                                grpc_slice_hash(method));
       for (probes = 0; chand->registered_methods[(hash + probes) % slots]
                            .server_registered_method != NULL;
            probes++)
diff --git a/src/core/lib/transport/metadata.h b/src/core/lib/transport/metadata.h
index ede09d7d76..fcd1c9222f 100644
--- a/src/core/lib/transport/metadata.h
+++ b/src/core/lib/transport/metadata.h
@@ -113,11 +113,9 @@ grpc_mdelem *grpc_mdelem_ref(grpc_mdelem *md);
 void grpc_mdelem_unref(grpc_exec_ctx *exec_ctx, grpc_mdelem *md);
 #endif
 
-#define GRPC_MDSTR_LENGTH(s) (GRPC_SLICE_LENGTH(s->slice))
-
 /* We add 32 bytes of padding as per RFC-7540 section 6.5.2. */
 #define GRPC_MDELEM_LENGTH(e) \
-  (GRPC_MDSTR_LENGTH((e)->key) + GRPC_MDSTR_LENGTH((e)->value) + 32)
+  (GRPC_SLICE_LENGTH((e)->key) + GRPC_SLICE_LENGTH((e)->value) + 32)
 
 #define GRPC_MDSTR_KV_HASH(k_hash, v_hash) (GPR_ROTL((k_hash), 2) ^ (v_hash))