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-rw-r--r--plugins/framing_json.c279
-rw-r--r--plugins/framing_json.md16
-rw-r--r--plugins/makefile2
3 files changed, 296 insertions, 1 deletions
diff --git a/plugins/framing_json.c b/plugins/framing_json.c
new file mode 100644
index 0000000..677e4e7
--- /dev/null
+++ b/plugins/framing_json.c
@@ -0,0 +1,279 @@
+#include <stdio.h>
+#include <ctype.h>
+#include <string.h>
+
+#include "../websocksy.h"
+
+static ssize_t json_length(char* data, size_t length);
+static ssize_t json_length_string(char* data, size_t length);
+
+static ssize_t json_length_array(char* data, size_t length){
+ size_t current_offset = 1;
+ int64_t next_length = 0;
+
+ if(!length){
+ return 0;
+ }
+
+ if(data[0] != '['){
+ return -1;
+ }
+
+ do{
+ //skip whitespace
+ for(; current_offset < length && isspace(data[current_offset]); current_offset++){
+ }
+
+ //empty array
+ if(!next_length && data[current_offset] == ']'){
+ break;
+ }
+
+ //get length
+ next_length = json_length(data + current_offset, length - current_offset);
+ if(next_length <= 0){
+ return next_length;
+ }
+
+ current_offset += next_length;
+ //check for end or ,
+ for(; current_offset < length && isspace(data[current_offset]); current_offset++){
+ }
+ //the ordering matters, check for complete array before checking for eod
+ if(data[current_offset] == ']'){
+ break;
+ }
+ if(current_offset >= length){
+ return 0;
+ }
+ if(data[current_offset] != ','){
+ break;
+ }
+ current_offset++;
+ } while(current_offset < length);
+
+ if(data[current_offset] == ']'){
+ return current_offset + 1;
+ }
+
+ return -1;
+}
+
+static ssize_t json_length_object(char* data, size_t length){
+ size_t current_offset = 1;
+ int64_t next_length = 0;
+
+ if(!length){
+ return 0;
+ }
+
+ if(data[0] != '{'){
+ return -1;
+ }
+
+ do{
+ //skip whitespace
+ for(; current_offset < length && isspace(data[current_offset]); current_offset++){
+ }
+
+ //empty object
+ if(!next_length && data[current_offset] == '}'){
+ break;
+ }
+
+ //get key string length
+ next_length = json_length_string(data + current_offset, length - current_offset);
+ if(next_length <= 0){
+ return next_length;
+ }
+
+ current_offset += next_length;
+ //find colon
+ for(; current_offset < length && isspace(data[current_offset]); current_offset++){
+ }
+ if(current_offset >= length - 1){ //need one more character
+ return 0;
+ }
+ else if(data[current_offset] != ':'){
+ return -1;
+ }
+ current_offset++;
+
+ //get value length
+ next_length = json_length(data + current_offset, length - current_offset);
+ if(next_length <= 0){
+ return next_length;
+ }
+
+ current_offset += next_length;
+ //check for end or ,
+ for(; current_offset < length && isspace(data[current_offset]); current_offset++){
+ }
+ //the ordering matters, check for complete object before checking for eod
+ if(data[current_offset] == '}'){
+ break;
+ }
+ if(current_offset >= length){
+ return 0;
+ }
+ if(data[current_offset] != ','){
+ break;
+ }
+ current_offset++;
+ } while(current_offset < length);
+
+ if(data[current_offset] == '}'){
+ return current_offset + 1;
+ }
+ return -1;
+}
+
+static ssize_t json_length_string(char* data, size_t length){
+ size_t string_length = 0;
+
+ if(!length){
+ return 0;
+ }
+
+ if(data[0] != '"'){
+ return -1;
+ }
+
+ //find terminating quotation mark not preceded by escape
+ for(string_length = 1; string_length < length
+ && isprint(data[string_length])
+ && (data[string_length] != '"' || data[string_length - 1] == '\\'); string_length++){
+ }
+
+ //complete string found
+ if(data[string_length] == '"' && data[string_length - 1] != '\\'){
+ return string_length + 1;
+ }
+
+ //still missing data
+ if(string_length >= length){
+ return 0;
+ }
+
+ //anything else
+ return -1;
+}
+
+static ssize_t json_length_value(char* data, size_t length){
+ size_t value_length = 0;
+
+ if(!length){
+ return 0;
+ }
+
+ if(data[0] == '-' || isdigit(data[0])){
+ //a number consisting of [minus] int [.int] [eE[+-]]
+ //terminator (comma, space, eod, eoa, eoo)
+ //since this is not a full parser, just ensure all characters are from that general set...
+ for(value_length = 1; value_length < length &&
+ (isdigit(data[value_length])
+ || data[value_length] == '+'
+ || data[value_length] == '-'
+ || data[value_length] == '.'
+ || tolower(data[value_length]) == 'e'); value_length++){
+ }
+ if(data[value_length] == ','
+ || data[value_length] == ' '
+ || data[value_length] == '}'
+ || data[value_length] == ']'){
+ return value_length;
+ }
+ if(value_length >= length){
+ if(data[value_length - 1] == '.'
+ || tolower(data[value_length - 1]) == 'e'
+ || data[value_length - 1] == '-'
+ || data[value_length - 1] == '+'){
+ return 0;
+ }
+ //numbers can be a value on their own...
+ return value_length;
+ }
+ }
+
+ //match complete values
+ if(length >= 4 && !strncmp(data, "null", 4)){
+ return 4;
+ }
+ else if(length >= 4 && !strncmp(data, "true", 4)){
+ return 4;
+ }
+ else if(length >= 5 && !strncmp(data, "false", 5)){
+ return 5;
+ }
+
+ //match prefix values
+ if(length < 4 && !strncmp(data, "null", length)){
+ return 0;
+ }
+ else if(length < 4 && !strncmp(data, "true", length)){
+ return 0;
+ }
+ else if(length < 5 && !strncmp(data, "false", length)){
+ return 0;
+ }
+
+ //invalid value
+ return -1;
+}
+
+static ssize_t json_length(char* data, size_t length){
+ size_t total_length = 0, current_offset = 0;
+ ssize_t rv = 0;
+
+ if(!length){
+ return 0;
+ }
+
+ //advance to the first non-blank
+ for(current_offset = 0; current_offset < length && isspace(data[current_offset]); current_offset++){
+ }
+
+ switch(data[current_offset]){
+ case '[':
+ rv = json_length_array(data + current_offset, length - current_offset);
+ break;
+ case '{':
+ rv = json_length_object(data + current_offset, length - current_offset);
+ break;
+ case '"':
+ rv = json_length_string(data + current_offset, length - current_offset);
+ break;
+ default:
+ //false null true
+ //0-9 | - -> number
+ rv = json_length_value(data + current_offset, length - current_offset);
+ break;
+ }
+
+ if(rv <= 0){
+ return rv;
+ }
+
+ return current_offset + rv;
+}
+
+static int64_t framing_json(uint8_t* data, size_t length, size_t last_read, ws_operation* opcode, void** framing_data, const char* config){
+ ssize_t data_length = json_length(data, length);
+
+ if(data_length > 0){
+ *opcode = ws_frame_text;
+ return data_length;
+ }
+ //incomplete
+ else if(data_length == 0){
+ return 0;
+ }
+ //failed to parse as json, just dump it
+ else{
+ return length;
+ }
+}
+
+static void __attribute__((constructor)) init(){
+ core_register_framing("json", framing_json);
+}
diff --git a/plugins/framing_json.md b/plugins/framing_json.md
new file mode 100644
index 0000000..c5a7e09
--- /dev/null
+++ b/plugins/framing_json.md
@@ -0,0 +1,16 @@
+# The `json` framing function
+
+The `json` framing function segments the peer stream at boundaries defined by complete JSON
+entities (Objects, Arrays, Strings or Values) and forwards these as text frames.
+
+For example, on encountering the start of a JSON object at the beginning of the stream, it will read from the
+peer until that objects closing brace and the send the entire object as a single text frame.
+
+The plugin does not implement a full parser and performs only rudimentary syntactic analysis to determine
+the end of the current entity. When encountering an error, the entire buffer is forwarded as a binary frame.
+It is possible to construct erroneous JSON objects that pass the parser without an error, however any
+syntactically correct object should be forwarded correctly (please file a bug with an example otherwise).
+
+## Configuration
+
+The `json` framing function does not require any configuration.
diff --git a/plugins/makefile b/plugins/makefile
index feab4cd..b09466d 100644
--- a/plugins/makefile
+++ b/plugins/makefile
@@ -1,5 +1,5 @@
.PHONY: all clean
-PLUGINS = backend_file.so framing_fixedlength.so
+PLUGINS = backend_file.so framing_fixedlength.so framing_json.so
CFLAGS += -fPIC -g -I../
LDFLAGS += -shared
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-22 16:53:13 +0000