Move source files to src/

src/jv_parse.c

@@ -0,0 +1,852 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include "jv.h"
+#include "jv_dtoa.h"
+#include "jv_unicode.h"
+#include "jv_alloc.h"
+#include "jv_dtoa.h"
+
+typedef const char* presult;
+
+#define TRY(x) do {presult msg__ = (x); if (msg__) return msg__; } while(0)
+#ifdef __GNUC__
+#define pfunc __attribute__((warn_unused_result)) presult
+#else
+#define pfunc presult
+#endif
+
+enum last_seen {
+  JV_LAST_NONE = 0,
+  JV_LAST_OPEN_ARRAY = '[',
+  JV_LAST_OPEN_OBJECT = '{',
+  JV_LAST_COLON = ':',
+  JV_LAST_COMMA = ',',
+  JV_LAST_VALUE = 'V',
+};
+
+struct jv_parser {
+  const char* curr_buf;
+  int curr_buf_length;
+  int curr_buf_pos;
+  int curr_buf_is_partial;
+  int eof;
+  unsigned bom_strip_position;
+
+  int flags;
+
+  jv* stack;                   // parser
+  int stackpos;                // parser
+  int stacklen;                // both (optimization; it's really pathlen for streaming)
+  jv path;                     // streamer
+  enum last_seen last_seen;    // streamer
+  jv output;                   // streamer
+  jv next;                     // both
+
+  char* tokenbuf;
+  int tokenpos;
+  int tokenlen;
+
+  int line, column;
+
+  struct dtoa_context dtoa;
+
+  enum {
+    JV_PARSER_NORMAL,
+    JV_PARSER_STRING,
+    JV_PARSER_STRING_ESCAPE,
+    JV_PARSER_WAITING_FOR_RS // parse error, waiting for RS
+  } st;
+  unsigned int last_ch_was_ws:1;
+};
+
+
+static void parser_init(struct jv_parser* p, int flags) {
+  p->flags = flags;
+  if ((p->flags & JV_PARSE_STREAMING)) {
+    p->path = jv_array();
+  } else {
+    p->path = jv_invalid();
+    p->flags &= ~(JV_PARSE_STREAM_ERRORS);
+  }
+  p->stack = 0;
+  p->stacklen = p->stackpos = 0;
+  p->last_seen = JV_LAST_NONE;
+  p->output = jv_invalid();
+  p->next = jv_invalid();
+  p->tokenbuf = 0;
+  p->tokenlen = p->tokenpos = 0;
+  if ((p->flags & JV_PARSE_SEQ))
+    p->st = JV_PARSER_WAITING_FOR_RS;
+  else
+    p->st = JV_PARSER_NORMAL;
+  p->eof = 0;
+  p->curr_buf = 0;
+  p->curr_buf_length = p->curr_buf_pos = p->curr_buf_is_partial = 0;
+  p->bom_strip_position = 0;
+  p->last_ch_was_ws = 0;
+  p->line = 1;
+  p->column = 0;
+  jvp_dtoa_context_init(&p->dtoa);
+}
+
+static void parser_reset(struct jv_parser* p) {
+  if ((p->flags & JV_PARSE_STREAMING)) {
+    jv_free(p->path);
+    p->path = jv_array();
+    p->stacklen = 0;
+  }
+  p->last_seen = JV_LAST_NONE;
+  jv_free(p->output);
+  p->output = jv_invalid();
+  jv_free(p->next);
+  p->next = jv_invalid();
+  for (int i=0; i<p->stackpos; i++)
+    jv_free(p->stack[i]);
+  p->stackpos = 0;
+  p->tokenpos = 0;
+  p->st = JV_PARSER_NORMAL;
+}
+
+static void parser_free(struct jv_parser* p) {
+  parser_reset(p);
+  jv_free(p->path);
+  jv_free(p->output);
+  jv_mem_free(p->stack);
+  jv_mem_free(p->tokenbuf);
+  jvp_dtoa_context_free(&p->dtoa);
+}
+
+static pfunc value(struct jv_parser* p, jv val) {
+  if ((p->flags & JV_PARSE_STREAMING)) {
+    if (jv_is_valid(p->next) || p->last_seen == JV_LAST_VALUE)
+      return "Expected separator between values";
+    if (p->stacklen > 0)
+      p->last_seen = JV_LAST_VALUE;
+    else
+      p->last_seen = JV_LAST_NONE;
+  } else {
+    if (jv_is_valid(p->next)) return "Expected separator between values";
+  }
+  jv_free(p->next);
+  p->next = val;
+  return 0;
+}
+
+static void push(struct jv_parser* p, jv v) {
+  assert(p->stackpos <= p->stacklen);
+  if (p->stackpos == p->stacklen) {
+    p->stacklen = p->stacklen * 2 + 10;
+    p->stack = jv_mem_realloc(p->stack, p->stacklen * sizeof(jv));
+  }
+  assert(p->stackpos < p->stacklen);
+  p->stack[p->stackpos++] = v;
+}
+
+static pfunc parse_token(struct jv_parser* p, char ch) {
+  switch (ch) {
+  case '[':
+    if (jv_is_valid(p->next)) return "Expected separator between values";
+    push(p, jv_array());
+    break;
+
+  case '{':
+    if (jv_is_valid(p->next)) return "Expected separator between values";
+    push(p, jv_object());
+    break;
+
+  case ':':
+    if (!jv_is_valid(p->next))
+      return "Expected string key before ':'";
+    if (p->stackpos == 0 || jv_get_kind(p->stack[p->stackpos-1]) != JV_KIND_OBJECT)
+      return "':' not as part of an object";
+    if (jv_get_kind(p->next) != JV_KIND_STRING)
+      return "Object keys must be strings";
+    push(p, p->next);
+    p->next = jv_invalid();
+    break;
+
+  case ',':
+    if (!jv_is_valid(p->next))
+      return "Expected value before ','";
+    if (p->stackpos == 0)
+      return "',' not as part of an object or array";
+    if (jv_get_kind(p->stack[p->stackpos-1]) == JV_KIND_ARRAY) {
+      p->stack[p->stackpos-1] = jv_array_append(p->stack[p->stackpos-1], p->next);
+      p->next = jv_invalid();
+    } else if (jv_get_kind(p->stack[p->stackpos-1]) == JV_KIND_STRING) {
+      assert(p->stackpos > 1 && jv_get_kind(p->stack[p->stackpos-2]) == JV_KIND_OBJECT);
+      p->stack[p->stackpos-2] = jv_object_set(p->stack[p->stackpos-2],
+                                              p->stack[p->stackpos-1], p->next);
+      p->stackpos--;
+      p->next = jv_invalid();
+    } else {
+      // this case hits on input like {"a", "b"}
+      return "Objects must consist of key:value pairs";
+    }
+    break;
+
+  case ']':
+    if (p->stackpos == 0 || jv_get_kind(p->stack[p->stackpos-1]) != JV_KIND_ARRAY)
+      return "Unmatched ']'";
+    if (jv_is_valid(p->next)) {
+      p->stack[p->stackpos-1] = jv_array_append(p->stack[p->stackpos-1], p->next);
+      p->next = jv_invalid();
+    } else {
+      if (jv_array_length(jv_copy(p->stack[p->stackpos-1])) != 0) {
+        // this case hits on input like [1,2,3,]
+        return "Expected another array element";
+      }
+    }
+    jv_free(p->next);
+    p->next = p->stack[--p->stackpos];
+    break;
+
+  case '}':
+    if (p->stackpos == 0)
+      return "Unmatched '}'";
+    if (jv_is_valid(p->next)) {
+      if (jv_get_kind(p->stack[p->stackpos-1]) != JV_KIND_STRING)
+        return "Objects must consist of key:value pairs";
+      assert(p->stackpos > 1 && jv_get_kind(p->stack[p->stackpos-2]) == JV_KIND_OBJECT);
+      p->stack[p->stackpos-2] = jv_object_set(p->stack[p->stackpos-2],
+                                              p->stack[p->stackpos-1], p->next);
+      p->stackpos--;
+      p->next = jv_invalid();
+    } else {
+      if (jv_get_kind(p->stack[p->stackpos-1]) != JV_KIND_OBJECT)
+        return "Unmatched '}'";
+      if (jv_object_length(jv_copy(p->stack[p->stackpos-1])) != 0)
+        return "Expected another key-value pair";
+    }
+    jv_free(p->next);
+    p->next = p->stack[--p->stackpos];
+    break;
+  }
+  return 0;
+}
+
+static pfunc stream_token(struct jv_parser* p, char ch) {
+  jv_kind k;
+  jv last;
+
+  switch (ch) {
+  case '[':
+    if (jv_is_valid(p->next))
+      return "Expected a separator between values";
+    p->path = jv_array_append(p->path, jv_number(0)); // push
+    p->last_seen = JV_LAST_OPEN_ARRAY;
+    p->stacklen++;
+    break;
+
+  case '{':
+    if (p->last_seen == JV_LAST_VALUE)
+      return "Expected a separator between values";
+    // Push object key: null, since we don't know it yet
+    p->path = jv_array_append(p->path, jv_null()); // push
+    p->last_seen = JV_LAST_OPEN_OBJECT;
+    p->stacklen++;
+    break;
+
+  case ':':
+    if (p->stacklen == 0 || jv_get_kind(jv_array_get(jv_copy(p->path), p->stacklen - 1)) == JV_KIND_NUMBER)
+      return "':' not as part of an object";
+    if (!jv_is_valid(p->next) || p->last_seen == JV_LAST_NONE)
+      return "Expected string key before ':'";
+    if (jv_get_kind(p->next) != JV_KIND_STRING)
+      return "Object keys must be strings";
+    if (p->last_seen != JV_LAST_VALUE)
+      return "':' should follow a key";
+    p->last_seen = JV_LAST_COLON;
+    p->path = jv_array_set(p->path, p->stacklen - 1, p->next);
+    p->next = jv_invalid();
+    break;
+
+  case ',':
+    if (p->last_seen != JV_LAST_VALUE)
+      return "Expected value before ','";
+    if (p->stacklen == 0)
+      return "',' not as part of an object or array";
+    last = jv_array_get(jv_copy(p->path), p->stacklen - 1);
+    k = jv_get_kind(last);
+    if (k == JV_KIND_NUMBER) {
+      int idx = jv_number_value(last);
+
+      if (jv_is_valid(p->next)) {
+        p->output = JV_ARRAY(jv_copy(p->path), p->next);
+        p->next = jv_invalid();
+      }
+      p->path = jv_array_set(p->path, p->stacklen - 1, jv_number(idx + 1));
+      p->last_seen = JV_LAST_COMMA;
+    } else if (k == JV_KIND_STRING) {
+      if (jv_is_valid(p->next)) {
+        p->output = JV_ARRAY(jv_copy(p->path), p->next);
+        p->next = jv_invalid();
+      }
+      p->path = jv_array_set(p->path, p->stacklen - 1, jv_true()); // ready for another name:value pair
+      p->last_seen = JV_LAST_COMMA;
+    } else {
+      assert(k == JV_KIND_NULL);
+      // this case hits on input like {,}
+      // make sure to handle input like {"a", "b"} and {"a":, ...}
+      jv_free(last);
+      return "Objects must consist of key:value pairs";
+    }
+    jv_free(last);
+    break;
+
+  case ']':
+    if (p->stacklen == 0)
+      return "Unmatched ']' at the top-level";
+    if (p->last_seen == JV_LAST_COMMA)
+      return "Expected another array element";
+    if (p->last_seen == JV_LAST_OPEN_ARRAY)
+      assert(!jv_is_valid(p->next));
+
+    last = jv_array_get(jv_copy(p->path), p->stacklen - 1);
+    k = jv_get_kind(last);
+    jv_free(last);
+
+    if (k != JV_KIND_NUMBER)
+      return "Unmatched ']' in the middle of an object";
+    if (jv_is_valid(p->next)) {
+      p->output = JV_ARRAY(jv_copy(p->path), p->next, jv_true());
+      p->next = jv_invalid();
+    } else if (p->last_seen != JV_LAST_OPEN_ARRAY) {
+      p->output = JV_ARRAY(jv_copy(p->path));
+    }
+
+    p->path = jv_array_slice(p->path, 0, --(p->stacklen)); // pop
+    //assert(!jv_is_valid(p->next));
+    jv_free(p->next);
+    p->next = jv_invalid();
+
+    if (p->last_seen == JV_LAST_OPEN_ARRAY)
+      p->output = JV_ARRAY(jv_copy(p->path), jv_array()); // Empty arrays are leaves
+
+    if (p->stacklen == 0)
+      p->last_seen = JV_LAST_NONE;
+    else
+      p->last_seen = JV_LAST_VALUE;
+    break;
+
+  case '}':
+    if (p->stacklen == 0)
+      return "Unmatched '}' at the top-level";
+    if (p->last_seen == JV_LAST_COMMA)
+      return "Expected another key:value pair";
+    if (p->last_seen == JV_LAST_OPEN_OBJECT)
+      assert(!jv_is_valid(p->next));
+
+    last = jv_array_get(jv_copy(p->path), p->stacklen - 1);
+    k = jv_get_kind(last);
+    jv_free(last);
+    if (k == JV_KIND_NUMBER)
+      return "Unmatched '}' in the middle of an array";
+
+    if (jv_is_valid(p->next)) {
+      if (k != JV_KIND_STRING)
+        return "Objects must consist of key:value pairs";
+      p->output = JV_ARRAY(jv_copy(p->path), p->next, jv_true());
+      p->next = jv_invalid();
+    } else {
+      // Perhaps {"a":[]}
+      if (p->last_seen == JV_LAST_COLON)
+        // Looks like {"a":}
+        return "Missing value in key:value pair";
+      if (p->last_seen == JV_LAST_COMMA)
+        // Looks like {"a":0,}
+        return "Expected another key-value pair";
+      if (p->last_seen == JV_LAST_OPEN_ARRAY)
+        return "Unmatched '}' in the middle of an array";
+      if (p->last_seen != JV_LAST_VALUE && p->last_seen != JV_LAST_OPEN_OBJECT)
+        return "Unmatched '}'";
+      if (p->last_seen != JV_LAST_OPEN_OBJECT)
+        p->output = JV_ARRAY(jv_copy(p->path));
+    }
+    p->path = jv_array_slice(p->path, 0, --(p->stacklen)); // pop
+    jv_free(p->next);
+    p->next = jv_invalid();
+
+    if (p->last_seen == JV_LAST_OPEN_OBJECT)
+      p->output = JV_ARRAY(jv_copy(p->path), jv_object()); // Empty arrays are leaves
+
+    if (p->stacklen == 0)
+      p->last_seen = JV_LAST_NONE;
+    else
+      p->last_seen = JV_LAST_VALUE;
+    break;
+  }
+  return 0;
+}
+
+static void tokenadd(struct jv_parser* p, char c) {
+  assert(p->tokenpos <= p->tokenlen);
+  if (p->tokenpos == p->tokenlen) {
+    p->tokenlen = p->tokenlen*2 + 256;
+    p->tokenbuf = jv_mem_realloc(p->tokenbuf, p->tokenlen);
+  }
+  assert(p->tokenpos < p->tokenlen);
+  p->tokenbuf[p->tokenpos++] = c;
+}
+
+static int unhex4(char* hex) {
+  int r = 0;
+  for (int i=0; i<4; i++) {
+    char c = *hex++;
+    int n;
+    if ('0' <= c && c <= '9') n = c - '0';
+    else if ('a' <= c && c <= 'f') n = c - 'a' + 10;
+    else if ('A' <= c && c <= 'F') n = c - 'A' + 10;
+    else return -1;
+    r <<= 4;
+    r |= n;
+  }
+  return r;
+}
+
+static pfunc found_string(struct jv_parser* p) {
+  char* in = p->tokenbuf;
+  char* out = p->tokenbuf;
+  char* end = p->tokenbuf + p->tokenpos;
+
+  while (in < end) {
+    char c = *in++;
+    if (c == '\\') {
+      if (in >= end)
+        return "Expected escape character at end of string";
+      c = *in++;
+      switch (c) {
+      case '\\':
+      case '"':
+      case '/': *out++ = c;    break;
+      case 'b': *out++ = '\b'; break;
+      case 'f': *out++ = '\f'; break;
+      case 't': *out++ = '\t'; break;
+      case 'n': *out++ = '\n'; break;
+      case 'r': *out++ = '\r'; break;
+
+      case 'u':
+        /* ahh, the complicated case */
+        if (in + 4 > end)
+          return "Invalid \\uXXXX escape";
+        int hexvalue = unhex4(in);
+        if (hexvalue < 0)
+          return "Invalid characters in \\uXXXX escape";
+        unsigned long codepoint = (unsigned long)hexvalue;
+        in += 4;
+        if (0xD800 <= codepoint && codepoint <= 0xDBFF) {
+          /* who thought UTF-16 surrogate pairs were a good idea? */
+          if (in + 6 > end || in[0] != '\\' || in[1] != 'u')
+            return "Invalid \\uXXXX\\uXXXX surrogate pair escape";
+          unsigned long surrogate = unhex4(in+2);
+          if (!(0xDC00 <= surrogate && surrogate <= 0xDFFF))
+            return "Invalid \\uXXXX\\uXXXX surrogate pair escape";
+          in += 6;
+          codepoint = 0x10000 + (((codepoint - 0xD800) << 10)
+                                 |(surrogate - 0xDC00));
+        }
+        if (codepoint > 0x10FFFF)
+          codepoint = 0xFFFD; // U+FFFD REPLACEMENT CHARACTER
+        out += jvp_utf8_encode(codepoint, out);
+        break;
+
+      default:
+        return "Invalid escape";
+      }
+    } else {
+      if (c > 0 && c < 0x001f)
+        return "Invalid string: control characters from U+0000 through U+001F must be escaped";
+      *out++ = c;
+    }
+  }
+  TRY(value(p, jv_string_sized(p->tokenbuf, out - p->tokenbuf)));
+  p->tokenpos = 0;
+  return 0;
+}
+
+static pfunc check_literal(struct jv_parser* p) {
+  if (p->tokenpos == 0) return 0;
+
+  const char* pattern = 0;
+  int plen;
+  jv v;
+  switch (p->tokenbuf[0]) {
+  case 't': pattern = "true"; plen = 4; v = jv_true(); break;
+  case 'f': pattern = "false"; plen = 5; v = jv_false(); break;
+  case 'n': pattern = "null"; plen = 4; v = jv_null(); break;
+  }
+  if (pattern) {
+    if (p->tokenpos != plen) return "Invalid literal";
+    for (int i=0; i<plen; i++)
+      if (p->tokenbuf[i] != pattern[i])
+        return "Invalid literal";
+    TRY(value(p, v));
+  } else {
+    // FIXME: better parser
+    p->tokenbuf[p->tokenpos] = 0; // FIXME: invalid
+    char* end = 0;
+    double d = jvp_strtod(&p->dtoa, p->tokenbuf, &end);
+    if (end == 0 || *end != 0)
+      return "Invalid numeric literal";
+    TRY(value(p, jv_number(d)));
+  }
+  p->tokenpos = 0;
+  return 0;
+}
+
+typedef enum {
+  LITERAL,
+  WHITESPACE,
+  STRUCTURE,
+  QUOTE,
+  INVALID
+} chclass;
+
+static chclass classify(char c) {
+  switch (c) {
+  case ' ':
+  case '\t':
+  case '\r':
+  case '\n':
+    return WHITESPACE;
+  case '"':
+    return QUOTE;
+  case '[':
+  case ',':
+  case ']':
+  case '{':
+  case ':':
+  case '}':
+    return STRUCTURE;
+  default:
+    return LITERAL;
+  }
+}
+
+
+static const presult OK = "output produced";
+
+static int parse_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 int stream_check_done(struct jv_parser* p, jv* out) {
+  if (p->stacklen == 0 && jv_is_valid(p->next)) {
+    *out = JV_ARRAY(jv_copy(p->path),p->next);
+    p->next = jv_invalid();
+    return 1;
+  } else if (jv_is_valid(p->output)) {
+    if (jv_array_length(jv_copy(p->output)) > 2) {
+      // At end of an array or object, necessitating one more output by
+      // which to indicate this
+      *out = jv_array_slice(jv_copy(p->output), 0, 2);
+      p->output = jv_array_slice(p->output, 0, 1);      // arrange one more output
+    } else {
+      // No further processing needed
+      *out = p->output;
+      p->output = jv_invalid();
+    }
+    return 1;
+  } else {
+    return 0;
+  }
+}
+
+static int parse_check_truncation(struct jv_parser* p) {
+  return ((p->flags & JV_PARSE_SEQ) && !p->last_ch_was_ws && (p->stackpos > 0 || p->tokenpos > 0 || jv_get_kind(p->next) == JV_KIND_NUMBER));
+}
+
+static int stream_check_truncation(struct jv_parser* p) {
+  jv_kind k = jv_get_kind(p->next);
+  return (p->stacklen > 0 || k == JV_KIND_NUMBER || k == JV_KIND_TRUE || k == JV_KIND_FALSE || k == JV_KIND_NULL);
+}
+
+static int parse_is_top_num(struct jv_parser* p) {
+  return (p->stackpos == 0 && jv_get_kind(p->next) == JV_KIND_NUMBER);
+}
+
+static int stream_is_top_num(struct jv_parser* p) {
+  return (p->stacklen == 0 && jv_get_kind(p->next) == JV_KIND_NUMBER);
+}
+
+#define check_done(p, o) \
+   (((p)->flags & JV_PARSE_STREAMING) ? stream_check_done((p), (o)) : parse_check_done((p), (o)))
+
+#define token(p, ch) \
+   (((p)->flags & JV_PARSE_STREAMING) ? stream_token((p), (ch)) : parse_token((p), (ch)))
+
+#define check_truncation(p) \
+   (((p)->flags & JV_PARSE_STREAMING) ? stream_check_truncation((p)) : parse_check_truncation((p)))
+
+#define is_top_num(p) \
+   (((p)->flags & JV_PARSE_STREAMING) ? stream_is_top_num((p)) : parse_is_top_num((p)))
+
+static pfunc scan(struct jv_parser* p, char ch, jv* out) {
+  p->column++;
+  if (ch == '\n') {
+    p->line++;
+    p->column = 0;
+  }
+  if (ch == '\036' /* ASCII RS; see draft-ietf-json-sequence-07 */) {
+    if (check_truncation(p)) {
+      if (check_literal(p) == 0 && is_top_num(p))
+        return "Potentially truncated top-level numeric value";
+      return "Truncated value";
+    }
+    TRY(check_literal(p));
+    if (p->st == JV_PARSER_NORMAL && check_done(p, out))
+      return OK;
+    // shouldn't happen?
+    assert(!jv_is_valid(*out));
+    parser_reset(p);
+    jv_free(*out);
+    *out = jv_invalid();
+    return OK;
+  }
+  presult answer = 0;
+  p->last_ch_was_ws = 0;
+  if (p->st == JV_PARSER_NORMAL) {
+    chclass cls = classify(ch);
+    if (cls == WHITESPACE)
+      p->last_ch_was_ws = 1;
+    if (cls != LITERAL) {
+      TRY(check_literal(p));
+      if (check_done(p, out)) answer = OK;
+    }
+    switch (cls) {
+    case LITERAL:
+      tokenadd(p, ch);
+      break;
+    case WHITESPACE:
+      break;
+    case QUOTE:
+      p->st = JV_PARSER_STRING;
+      break;
+    case STRUCTURE:
+      TRY(token(p, ch));
+      break;
+    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) {
+        p->st = JV_PARSER_STRING_ESCAPE;
+      } else {
+        p->st = JV_PARSER_STRING;
+      }
+    }
+  }
+  return answer;
+}
+
+struct jv_parser* jv_parser_new(int flags) {
+  struct jv_parser* p = jv_mem_alloc(sizeof(struct jv_parser));
+  parser_init(p, flags);
+  p->flags = flags;
+  return p;
+}
+
+void jv_parser_free(struct jv_parser* p) {
+  parser_free(p);
+  jv_mem_free(p);
+}
+
+static const unsigned char UTF8_BOM[] = {0xEF,0xBB,0xBF};
+
+int jv_parser_remaining(struct jv_parser* p) {
+  if (p->curr_buf == 0)
+    return 0;
+  return (p->curr_buf_length - p->curr_buf_pos);
+}
+
+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");
+  while (length > 0 && p->bom_strip_position < sizeof(UTF8_BOM)) {
+    if ((unsigned char)*buf == UTF8_BOM[p->bom_strip_position]) {
+      // matched a BOM character
+      buf++;
+      length--;
+      p->bom_strip_position++;
+    } else {
+      if (p->bom_strip_position == 0) {
+        // no BOM in this document
+        p->bom_strip_position = sizeof(UTF8_BOM);
+      } else {
+        // malformed BOM (prefix present, rest missing)
+        p->bom_strip_position = 0xff;
+      }
+    }
+  }
+  p->curr_buf = buf;
+  p->curr_buf_length = length;
+  p->curr_buf_pos = 0;
+  p->curr_buf_is_partial = is_partial;
+}
+
+static jv make_error(struct jv_parser*, const char *, ...) JV_PRINTF_LIKE(2, 3);
+
+static jv make_error(struct jv_parser* p, const char *fmt, ...) {
+  va_list ap;
+  va_start(ap, fmt);
+  jv e = jv_string_vfmt(fmt, ap);
+  va_end(ap);
+  if ((p->flags & JV_PARSE_STREAM_ERRORS))
+    return JV_ARRAY(e, jv_copy(p->path));
+  return jv_invalid_with_msg(e);
+}
+
+jv jv_parser_next(struct jv_parser* p) {
+  if (p->eof)
+    return jv_invalid();
+  if (!p->curr_buf)
+    return jv_invalid(); // Need a buffer
+  if (p->bom_strip_position == 0xff) {
+    if (!(p->flags & JV_PARSE_SEQ))
+      return jv_invalid_with_msg(jv_string("Malformed BOM"));
+    p->st =JV_PARSER_WAITING_FOR_RS;
+    parser_reset(p);
+  }
+  jv value = jv_invalid();
+  if ((p->flags & JV_PARSE_STREAMING) && stream_check_done(p, &value))
+    return value;
+  char ch;
+  presult msg = 0;
+  while (!msg && p->curr_buf_pos < p->curr_buf_length) {
+    ch = p->curr_buf[p->curr_buf_pos++];
+    if (p->st == JV_PARSER_WAITING_FOR_RS) {
+      if (ch == '\n') {
+        p->line++;
+        p->column = 0;
+      } else {
+        p->column++;
+      }
+      if (ch == '\036')
+        p->st = JV_PARSER_NORMAL;
+      continue; // need to resync, wait for RS
+    }
+    msg = scan(p, ch, &value);
+  }
+  if (msg == OK) {
+    return value;
+  } else if (msg) {
+    jv_free(value);
+    if (ch != '\036' && (p->flags & JV_PARSE_SEQ)) {
+      // Skip to the next RS
+      p->st = JV_PARSER_WAITING_FOR_RS;
+      value = make_error(p, "%s at line %d, column %d (need RS to resync)", msg, p->line, p->column);
+      parser_reset(p);
+      return value;
+    }
+    value = make_error(p, "%s at line %d, column %d", msg, p->line, p->column);
+    parser_reset(p);
+    if (!(p->flags & JV_PARSE_SEQ)) {
+      // We're not parsing a JSON text sequence; throw this buffer away.
+      // XXX We should fail permanently here.
+      p->curr_buf = 0;
+      p->curr_buf_pos = 0;
+    } // Else ch must be RS; don't clear buf so we can start parsing again after this ch
+    return value;
+  } else if (p->curr_buf_is_partial) {
+    assert(p->curr_buf_pos == p->curr_buf_length);
+    // need another buffer
+    return jv_invalid();
+  } else {
+    // at EOF
+    p->eof = 1;
+    assert(p->curr_buf_pos == p->curr_buf_length);
+    jv_free(value);
+    if (p->st == JV_PARSER_WAITING_FOR_RS)
+      return make_error(p, "Unfinished abandoned text at EOF at line %d, column %d", p->line, p->column);
+    if (p->st != JV_PARSER_NORMAL) {
+      value = make_error(p, "Unfinished string at EOF at line %d, column %d", p->line, p->column);
+      parser_reset(p);
+      p->st = JV_PARSER_WAITING_FOR_RS;
+      return value;
+    }
+    if ((msg = check_literal(p))) {
+      value = make_error(p, "%s at EOF at line %d, column %d", msg, p->line, p->column);
+      parser_reset(p);
+      p->st = JV_PARSER_WAITING_FOR_RS;
+      return value;
+    }
+    if (((p->flags & JV_PARSE_STREAMING) && p->stacklen != 0) ||
+        (!(p->flags & JV_PARSE_STREAMING) && p->stackpos != 0)) {
+      value = make_error(p, "Unfinished JSON term at EOF at line %d, column %d", p->line, p->column);
+      parser_reset(p);
+      p->st = JV_PARSER_WAITING_FOR_RS;
+      return value;
+    }
+    // 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
+    if ((p->flags & JV_PARSE_STREAMING) && jv_is_valid(p->next)) {
+      value = JV_ARRAY(jv_copy(p->path), p->next); // except in streaming mode we've got to make it [path,value]
+    } else {
+      value = p->next;
+    }
+    p->next = jv_invalid();
+    if ((p->flags & JV_PARSE_SEQ) && !p->last_ch_was_ws && jv_get_kind(value) == JV_KIND_NUMBER) {
+      jv_free(value);
+      return make_error(p, "Potentially truncated top-level numeric value at EOF at line %d, column %d", p->line, p->column);
+    }
+    return value;
+  }
+}
+
+jv jv_parse_sized(const char* string, int length) {
+  struct jv_parser parser;
+  parser_init(&parser, 0);
+  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 {
+    // no value at all
+    jv_free(value);
+    value = jv_invalid_with_msg(jv_string("Expected JSON value"));
+  }
+  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;
+}
+
+jv jv_parse(const char* string) {
+  return jv_parse_sized(string, strlen(string));
+}