JSON stream parser.

Allow multiple values on input as concatenated JSON objects,
possibly separated by whitespace.

c/jv.c

@@ -103,6 +103,13 @@ jv jv_invalid_get_msg(jv inv) {
   return x;
 }
 
+int jv_invalid_has_msg(jv inv) {
+  jv msg = jv_invalid_get_msg(inv);
+  int r = jv_get_kind(msg) != JV_KIND_NULL;
+  jv_free(msg);
+  return r;
+}
+
 static void jvp_invalid_free(jv_complex* x) {
   if (jvp_refcnt_dec(x)) {
     jv_free(((jvp_invalid*)x->ptr)->errmsg);

c/jv.h

@@ -52,6 +52,8 @@ int jv_equal(jv, jv);
 jv jv_invalid();
 jv jv_invalid_with_msg(jv);
 jv jv_invalid_get_msg(jv);
+int jv_invalid_has_msg(jv);
+
 
 jv jv_null();
 jv jv_true();

c/jv_dtoa.h

@@ -1,4 +1,5 @@
-
+#ifndef JV_DTOA_H
+#define JV_DTOA_H
 #define Kmax 7
 
 struct Bigint;
@@ -18,3 +19,4 @@ void jvp_freedtoa(struct dtoa_context* C, char *s);
 
 #define JVP_DTOA_FMT_MAX_LEN 32
 char* jvp_dtoa_fmt(struct dtoa_context* C, register char *b, double x);
+#endif

c/jv_parse.c

@@ -22,11 +22,15 @@ void jv_parser_init(struct jv_parser* p) {
   p->tokenbuf = 0;
   p->tokenlen = p->tokenpos = 0;
   p->st = JV_PARSER_NORMAL;
+  p->curr_buf = 0;
+  p->curr_buf_length = p->curr_buf_pos = p->curr_buf_is_partial = 0;
   jvp_dtoa_context_init(&p->dtoa);
 }
 
 void jv_parser_free(struct jv_parser* p) {
   jv_free(p->next);
+  for (int i=0; i<p->stackpos; i++) 
+    jv_free(p->stack[i]);
   free(p->stack);
   free(p->tokenbuf);
   jvp_dtoa_context_free(&p->dtoa);
@@ -271,13 +275,25 @@ static chclass classify(char c) {
 }
 
 
+static presult OK = "output produced";
 
+static int check_done(struct jv_parser* p, jv* out) {
+  if (p->stackpos == 0 && jv_is_valid(p->next)) {
+    *out = p->next;
+    p->next = jv_invalid();
+    return 1;
+  } else {
+    return 0;
+  }
+}
 
-static pfunc scan(struct jv_parser* p, char ch) {
+static pfunc scan(struct jv_parser* p, char ch, jv* out) {
+  presult answer = 0;
   if (p->st == JV_PARSER_NORMAL) {
     chclass cls = classify(ch);
     if (cls != LITERAL) {
       TRY(check_literal(p));
+      if (check_done(p, out)) answer = OK;
     }
     switch (cls) {
     case LITERAL:
@@ -294,10 +310,12 @@ static pfunc scan(struct jv_parser* p, char ch) {
     case INVALID:
       return "Invalid character";
     }
+    if (check_done(p, out)) answer = OK;
   } else {
     if (ch == '"' && p->st == JV_PARSER_STRING) {
       TRY(found_string(p));
       p->st = JV_PARSER_NORMAL;
+      if (check_done(p, out)) answer = OK;
     } else {
       tokenadd(p, ch);
       if (ch == '\\' && p->st == JV_PARSER_STRING) {
@@ -307,43 +325,87 @@ static pfunc scan(struct jv_parser* p, char ch) {
       }
     }
   }
-  return 0;
+  return answer;
 }
 
-static pfunc finish(struct jv_parser* p) {
-  if (p->st != JV_PARSER_NORMAL)
-    return "Unfinished string";
-  TRY(check_literal(p));
+void jv_parser_set_buf(struct jv_parser* p, const char* buf, int length, int is_partial) {
+  assert((p->curr_buf == 0 || p->curr_buf_pos == p->curr_buf_length)
+         && "previous buffer not exhausted");
+  p->curr_buf = buf;
+  p->curr_buf_length = length;
+  p->curr_buf_pos = 0;
+  p->curr_buf_is_partial = is_partial;
+}
 
-  if (p->stackpos != 0)
-    return "Unfinished JSON term";
-  
-  // this will happen on the empty string
-  if (!jv_is_valid(p->next))
-    return "Expected JSON value";
-  
-  return 0;
+jv jv_parser_next(struct jv_parser* p) {
+  assert(p->curr_buf && "a buffer must be provided");
+  jv value;
+  presult msg = 0;
+  while (!msg && p->curr_buf_pos < p->curr_buf_length) {
+    char ch = p->curr_buf[p->curr_buf_pos++];
+    msg = scan(p, ch, &value);
+  }
+  if (msg == OK) {
+    return value;
+  } else if (msg) {
+    return jv_invalid_with_msg(jv_string(msg));
+  } else if (p->curr_buf_is_partial) {
+    assert(p->curr_buf_pos == p->curr_buf_length);
+    // need another buffer
+    return jv_invalid();
+  } else {
+    assert(p->curr_buf_pos == p->curr_buf_length);
+    // at EOF
+    if (p->st != JV_PARSER_NORMAL) 
+      return jv_invalid_with_msg(jv_string("Unfinished string"));
+    if ((msg = check_literal(p)))
+      return jv_invalid_with_msg(jv_string(msg));
+    if (p->stackpos != 0)
+      return jv_invalid_with_msg(jv_string("Unfinished JSON term"));
+    // p->next is either invalid (nothing here but no syntax error)
+    // or valid (this is the value). either way it's the thing to return
+    value = p->next;
+    p->next = jv_invalid();
+    return value;
+  }
 }
 
 jv jv_parse_sized(const char* string, int length) {
   struct jv_parser parser;
   jv_parser_init(&parser);
-
-  const char* p = string;
-  char ch;
-  presult msg = 0;
-  while (msg == 0 && p < string + length) {
-    ch = *p++;
-    msg = scan(&parser, ch);
-  }
-  if (msg == 0) msg = finish(&parser);
-  jv value;
-  if (msg) {
-    value = jv_invalid_with_msg(jv_string_fmt("%s (while parsing '%s')", msg, string));
+  jv_parser_set_buf(&parser, string, length, 0);
+  jv value = jv_parser_next(&parser);
+  if (jv_is_valid(value)) {
+    jv next = jv_parser_next(&parser);
+    if (jv_is_valid(next)) {
+      // multiple JSON values, we only wanted one
+      jv_free(value);
+      jv_free(next);
+      value = jv_invalid_with_msg(jv_string("Unexpected extra JSON values"));
+    } else if (jv_invalid_has_msg(jv_copy(next))) {
+      // parser error after the first JSON value
+      jv_free(value);
+      value = next;
+    } else {
+      // a single valid JSON value
+      jv_free(next);
+    }
+  } else if (jv_invalid_has_msg(jv_copy(value))) {
+    // parse error, we'll return it
   } else {
-    value = jv_copy(parser.next);
+    // no value at all
+    jv_free(value);
+    value = jv_invalid_with_msg(jv_string("Expected JSON value"));
   }
   jv_parser_free(&parser);
+
+  if (!jv_is_valid(value) && jv_invalid_has_msg(jv_copy(value))) {
+    jv msg = jv_invalid_get_msg(value);
+    value = jv_invalid_with_msg(jv_string_fmt("%s (while parsing '%s')",
+                                              jv_string_value(msg),
+                                              string));
+    jv_free(msg);
+  }
   return value;
 }
 

c/jv_parse.h

@@ -1,5 +1,12 @@
-
+#ifndef JV_PARSE_H
+#define JV_PARSE_H
+#include "jv_dtoa.h"
 struct jv_parser {
+  const char* curr_buf;
+  int curr_buf_length;
+  int curr_buf_pos;
+  int curr_buf_is_partial;
+
   jv* stack;
   int stackpos;
   int stacklen;
@@ -17,3 +24,11 @@ struct jv_parser {
     JV_PARSER_STRING_ESCAPE
   } st;
 };
+
+void jv_parser_init(struct jv_parser* p);
+void jv_parser_free(struct jv_parser* p);
+
+void jv_parser_set_buf(struct jv_parser* p, const char* buf, int length, int is_partial);
+
+jv jv_parser_next(struct jv_parser* p);
+#endif

c/jv_print.c

@@ -10,7 +10,7 @@ static void jv_dump_string(jv str, int ascii_only) {
   assert(jv_get_kind(str) == JV_KIND_STRING);
   const char* i = jv_string_value(str);
   const char* end = i + jv_string_length(jv_copy(str));
-  int c;
+  int c = 0;
   while ((i = jvp_utf8_next(i, end, &c))) {
     assert(c != -1);
     int unicode_escape = 0;

c/main.c

@@ -4,6 +4,7 @@
 #include "parser.tab.h"
 #include "builtin.h"
 #include "jv.h"
+#include "jv_parse.h"
 #include "locfile.h"
 
 int jq_parse(struct locfile* source, block* answer);
@@ -31,31 +32,6 @@ struct bytecode* jq_compile(const char* str) {
   return bc;
 }
 
-
-void run_program(struct bytecode* bc) {
-#if JQ_DEBUG
-  dump_disassembly(0, bc);
-  printf("\n");
-#endif
-  char buf[409600];
-  fgets(buf, sizeof(buf), stdin);
-  jv value = jv_parse(buf);
-  if (!jv_is_valid(value)) {
-    assert(0 && "couldn't parse input"); //FIXME
-  }
-  jq_init(bc, value);
-  jv result;
-  while (jv_is_valid(result = jq_next())) {
-    jv_dump(result);
-    printf("\n");
-  }
-  jv_free(result);
-  #if JQ_DEBUG
-  printf("end of results\n");
-  #endif
-  jq_teardown();
-}
-
 int skipline(const char* buf) {
   int p = 0;
   while (buf[p] == ' ' || buf[p] == '\t') p++;
@@ -128,7 +104,40 @@ int main(int argc, char* argv[]) {
   if (argc == 1) { run_tests(); return 0; }
   struct bytecode* bc = jq_compile(argv[1]);
   if (!bc) return 1;
-  run_program(bc);
+
+#if JQ_DEBUG
+  dump_disassembly(0, bc);
+  printf("\n");
+#endif
+
+  struct jv_parser parser;
+  jv_parser_init(&parser);
+  while (!feof(stdin)) {
+    char buf[4096];
+    if (!fgets(buf, sizeof(buf), stdin)) buf[0] = 0;
+    jv_parser_set_buf(&parser, buf, strlen(buf), !feof(stdin));
+    jv value;
+    while (jv_is_valid((value = jv_parser_next(&parser)))) {
+      jq_init(bc, value);
+      jv result;
+      while (jv_is_valid(result = jq_next())) {
+        jv_dump(result);
+        printf("\n");
+      }
+      jv_free(result);
+      jq_teardown();
+    }
+    if (jv_invalid_has_msg(jv_copy(value))) {
+      jv msg = jv_invalid_get_msg(value);
+      fprintf(stderr, "parse error: %s\n", jv_string_value(msg));
+      jv_free(msg);
+      break;
+    } else {
+      jv_free(value);
+    }
+  }
+  jv_parser_free(&parser);
+
   bytecode_free(bc);
   return 0;
 }