Patchwork [09/11] Add a JSON parser

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Submitter Anthony Liguori
Date Nov. 11, 2009, 5:29 p.m.
Message ID <1257960543-26373-9-git-send-email-aliguori@us.ibm.com>
Download mbox | patch
Permalink /patch/38150/
State New
Headers show

Comments

Anthony Liguori - Nov. 11, 2009, 5:29 p.m.
This is the third and final stage of the JSON parser.  It parses lexical tokens
performing grammar validation and creating the final QObject representation.  It
uses a recursive decent parser.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
---
 Makefile      |    2 +-
 json-parser.c |  560 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 json-parser.h |   22 +++
 3 files changed, 583 insertions(+), 1 deletions(-)
 create mode 100644 json-parser.c
 create mode 100644 json-parser.h

Patch

diff --git a/Makefile b/Makefile
index a2aab60..6d68a1f 100644
--- a/Makefile
+++ b/Makefile
@@ -136,7 +136,7 @@  obj-y += qemu-char.o aio.o savevm.o
 obj-y += msmouse.o ps2.o
 obj-y += qdev.o qdev-properties.o
 obj-y += qint.o qstring.o qdict.o qlist.o qfloat.o qbool.o json-lexer.o
-obj-y += json-streamer.o
+obj-y += json-streamer.o json-parser.o
 obj-y += qemu-config.o
 
 obj-$(CONFIG_BRLAPI) += baum.o
diff --git a/json-parser.c b/json-parser.c
new file mode 100644
index 0000000..a0c0dca
--- /dev/null
+++ b/json-parser.c
@@ -0,0 +1,560 @@ 
+/*
+ * JSON Parser 
+ *
+ * Copyright IBM, Corp. 2009
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ *
+ */
+
+#include <stdbool.h>
+
+#include "qemu-common.h"
+#include "qstring.h"
+#include "qint.h"
+#include "qdict.h"
+#include "qlist.h"
+#include "qfloat.h"
+#include "qbool.h"
+#include "json-parser.h"
+#include "json-lexer.h"
+
+typedef struct JSONParserContext
+{
+} JSONParserContext;
+
+#define BUG_ON(cond) assert(!(cond))
+
+/**
+ * TODO
+ *
+ * 0) make errors meaningful again
+ * 1) add geometry information to tokens
+ * 3) should we return a parsed size?
+ * 4) deal with premature EOI
+ */
+
+static QObject *parse_value(JSONParserContext *ctxt, QList **tokens, va_list *ap);
+
+/**
+ * Token manipulators
+ *
+ * tokens are dictionaries that contain a type, a string value, and geometry information
+ * about a token identified by the lexer.  These are routines that make working with
+ * these objects a bit easier.
+ */
+static const char *token_get_value(QObject *obj)
+{
+    return qdict_get_str(qobject_to_qdict(obj), "token");
+}
+
+static JSONTokenType token_get_type(QObject *obj)
+{
+    return qdict_get_int(qobject_to_qdict(obj), "type");
+}
+
+static int token_is_operator(QObject *obj, char op)
+{
+    const char *val;
+
+    if (token_get_type(obj) != JSON_OPERATOR) {
+        return 0;
+    }
+
+    val = token_get_value(obj);
+
+    return (val[0] == op) && (val[1] == 0);
+}
+
+static int token_is_keyword(QObject *obj, const char *value)
+{
+    if (token_get_type(obj) != JSON_KEYWORD) {
+        return 0;
+    }
+
+    return strcmp(token_get_value(obj), value) == 0;
+}
+
+static int token_is_escape(QObject *obj, const char *value)
+{
+    if (token_get_type(obj) != JSON_ESCAPE) {
+        return 0;
+    }
+
+    return (strcmp(token_get_value(obj), value) == 0);
+}
+
+/**
+ * Error handler
+ */
+static void parse_error(JSONParserContext *ctxt, QObject *token, const char *msg, ...)
+{
+    fprintf(stderr, "parse error: %s\n", msg);
+}
+
+/**
+ * String helpers
+ *
+ * These helpers are used to unescape strings.
+ */
+static void wchar_to_utf8(uint16_t wchar, char *buffer, size_t buffer_length)
+{
+    if (wchar <= 0x007F) {
+        BUG_ON(buffer_length < 2);
+
+        buffer[0] = wchar & 0x7F;
+        buffer[1] = 0;
+    } else if (wchar <= 0x07FF) {
+        BUG_ON(buffer_length < 3);
+
+        buffer[0] = 0xC0 | ((wchar >> 6) & 0x1F);
+        buffer[1] = 0x80 | (wchar & 0x3F);
+        buffer[2] = 0;
+    } else {
+        BUG_ON(buffer_length < 4);
+
+        buffer[0] = 0xE0 | ((wchar >> 12) & 0x0F);
+        buffer[1] = 0x80 | ((wchar >> 6) & 0x3F);
+        buffer[2] = 0x80 | (wchar & 0x3F);
+        buffer[3] = 0;
+    }
+}
+
+static int hex2decimal(char ch)
+{
+    if (ch >= '0' && ch <= '9') {
+        return (ch - '0');
+    } else if (ch >= 'a' && ch <= 'f') {
+        return 10 + (ch - 'a');
+    } else if (ch >= 'A' && ch <= 'F') {
+        return 10 + (ch - 'A');
+    }
+
+    return -1;
+}
+
+/**
+ * parse_string(): Parse a json string and return a QObject
+ *
+ *  string
+ *      ""
+ *      " chars "
+ *  chars
+ *      char
+ *      char chars
+ *  char
+ *      any-Unicode-character-
+ *          except-"-or-\-or-
+ *          control-character
+ *      \"
+ *      \\
+ *      \/
+ *      \b
+ *      \f
+ *      \n
+ *      \r
+ *      \t
+ *      \u four-hex-digits 
+ */
+static QString *qstring_from_escaped_str(JSONParserContext *ctxt, QObject *token)
+{
+    const char *ptr = token_get_value(token);
+    QString *str;
+    int double_quote = 1;
+
+    if (*ptr == '"') {
+        double_quote = 1;
+    } else {
+        double_quote = 0;
+    }
+    ptr++;
+
+    str = qstring_new();
+    while (*ptr && 
+           ((double_quote && *ptr != '"') || (!double_quote && *ptr != '\''))) {
+        if (*ptr == '\\') {
+            ptr++;
+
+            switch (*ptr) {
+            case '"':
+                qstring_append(str, "\"");
+                ptr++;
+                break;
+            case '\'':
+                qstring_append(str, "'");
+                ptr++;
+                break;
+            case '\\':
+                qstring_append(str, "\\");
+                ptr++;
+                break;
+            case '/':
+                qstring_append(str, "/");
+                ptr++;
+                break;
+            case 'b':
+                qstring_append(str, "\b");
+                ptr++;
+                break;
+            case 'n':
+                qstring_append(str, "\n");
+                ptr++;
+                break;
+            case 'r':
+                qstring_append(str, "\r");
+                ptr++;
+                break;
+            case 't':
+                qstring_append(str, "\t");
+                ptr++;
+                break;
+            case 'u': {
+                uint16_t unicode_char = 0;
+                char utf8_char[4];
+                int i = 0;
+
+                ptr++;
+
+                for (i = 0; i < 4; i++) {
+                    if (qemu_isxdigit(*ptr)) {
+                        unicode_char |= hex2decimal(*ptr) << ((3 - i) * 4);
+                    } else {
+                        parse_error(ctxt, token,
+                                    "invalid hex escape sequence in string");
+                        goto out;
+                    }
+                    ptr++;
+                }
+
+                wchar_to_utf8(unicode_char, utf8_char, sizeof(utf8_char));
+                qstring_append(str, utf8_char);
+            }   break;
+            default:
+                parse_error(ctxt, token, "invalid escape sequence in string");
+                goto out;
+            }
+        } else {
+            char dummy[2];
+
+            dummy[0] = *ptr++;
+            dummy[1] = 0;
+
+            qstring_append(str, dummy);
+        }
+    }
+
+    ptr++;
+
+    return str;
+
+out:
+    QDECREF(str);
+    return NULL;
+}
+
+/**
+ * Parsing rules
+ */
+static int parse_pair(JSONParserContext *ctxt, QDict *dict, QList **tokens, va_list *ap)
+{
+    QObject *key, *token = NULL, *value, *peek;
+    QList *working = qlist_copy(*tokens);
+
+    peek = qlist_peek(working);
+    key = parse_value(ctxt, &working, ap);
+    if (qobject_type(key) != QTYPE_QSTRING) {
+        parse_error(ctxt, peek, "key is not a string in object");
+        goto out;
+    }
+
+    token = qlist_pop(working);
+    if (!token_is_operator(token, ':')) {
+        parse_error(ctxt, token, "missing : in object pair");
+        goto out;
+    }
+
+    value = parse_value(ctxt, &working, ap);
+    if (value == NULL) {
+        parse_error(ctxt, token, "Missing value in dict");
+        goto out;
+    }
+
+    qdict_put_obj(dict, qstring_get_str(qobject_to_qstring(key)), value);
+
+    qobject_decref(token);
+    qobject_decref(key);
+    QDECREF(*tokens);
+    *tokens = working;
+
+    return 0;
+
+out:
+    qobject_decref(token);
+    qobject_decref(key);
+    QDECREF(working);
+
+    return -1;
+}
+
+static QObject *parse_object(JSONParserContext *ctxt, QList **tokens, va_list *ap)
+{
+    QDict *dict = NULL;
+    QObject *token, *peek;
+    QList *working = qlist_copy(*tokens);
+
+    token = qlist_pop(working);
+    if (!token_is_operator(token, '{')) {
+        goto out;
+    }
+    qobject_decref(token);
+    token = NULL;
+
+    dict = qdict_new();
+
+    peek = qlist_peek(working);
+    if (!token_is_operator(peek, '}')) {
+        if (parse_pair(ctxt, dict, &working, ap) == -1) {
+            goto out;
+        }
+
+        token = qlist_pop(working);
+        while (!token_is_operator(token, '}')) {
+            if (!token_is_operator(token, ',')) {
+                parse_error(ctxt, token, "expected separator in dict");
+                goto out;
+            }
+            qobject_decref(token);
+            token = NULL;
+
+            if (parse_pair(ctxt, dict, &working, ap) == -1) {
+                goto out;
+            }
+
+            token = qlist_pop(working);
+        }
+        qobject_decref(token);
+        token = NULL;
+    }
+
+    QDECREF(*tokens);
+    *tokens = working;
+
+    return QOBJECT(dict);
+
+out:
+    qobject_decref(token);
+    QDECREF(working);
+    QDECREF(dict);
+    return NULL;
+}
+
+static QObject *parse_array(JSONParserContext *ctxt, QList **tokens, va_list *ap)
+{
+    QList *list = NULL;
+    QObject *token, *peek;
+    QList *working = qlist_copy(*tokens);
+
+    token = qlist_pop(working);
+    if (!token_is_operator(token, '[')) {
+        goto out;
+    }
+    qobject_decref(token);
+    token = NULL;
+
+    list = qlist_new();
+
+    peek = qlist_peek(working);
+    if (!token_is_operator(peek, ']')) {
+        QObject *obj;
+
+        obj = parse_value(ctxt, &working, ap);
+        if (obj == NULL) {
+            parse_error(ctxt, token, "expecting value");
+            goto out;
+        }
+
+        qlist_append_obj(list, obj);
+
+        token = qlist_pop(working);
+        while (!token_is_operator(token, ']')) {
+            if (!token_is_operator(token, ',')) {
+                parse_error(ctxt, token, "expected separator in list");
+                goto out;
+            }
+
+            qobject_decref(token);
+            token = NULL;
+
+            obj = parse_value(ctxt, &working, ap);
+            if (obj == NULL) {
+                parse_error(ctxt, token, "expecting value");
+                goto out;
+            }
+
+            qlist_append_obj(list, obj);
+
+            token = qlist_pop(working);
+        }
+
+        qobject_decref(token);
+        token = NULL;
+    }
+
+    QDECREF(*tokens);
+    *tokens = working;
+
+    return QOBJECT(list);
+
+out:
+    qobject_decref(token);
+    QDECREF(working);
+    QDECREF(list);
+    return NULL;
+}
+
+static QObject *parse_keyword(JSONParserContext *ctxt, QList **tokens)
+{
+    QObject *token, *ret;
+    QList *working = qlist_copy(*tokens);
+
+    token = qlist_pop(working);
+
+    if (token_get_type(token) != JSON_KEYWORD) {
+        goto out;
+    }
+
+    if (token_is_keyword(token, "true")) {
+        ret = QOBJECT(qbool_from_int(true));
+    } else if (token_is_keyword(token, "false")) {
+        ret = QOBJECT(qbool_from_int(false));
+    } else {
+        parse_error(ctxt, token, "invalid keyword `%s'", token_get_value(token));
+        goto out;
+    }
+
+    qobject_decref(token);
+    QDECREF(*tokens);
+    *tokens = working;
+
+    return ret;
+
+out: 
+    qobject_decref(token);
+    QDECREF(working);
+
+    return NULL;
+}
+
+static QObject *parse_escape(JSONParserContext *ctxt, QList **tokens, va_list *ap)
+{
+    QObject *token = NULL, *obj;
+    QList *working = qlist_copy(*tokens);
+
+    if (ap == NULL) {
+        goto out;
+    }
+
+    token = qlist_pop(working);
+
+    if (token_is_escape(token, "%p")) {
+        obj = va_arg(*ap, QObject *);
+    } else if (token_is_escape(token, "%i")) {
+        obj = QOBJECT(qbool_from_int(va_arg(*ap, int)));
+    } else if (token_is_escape(token, "%d")) {
+        obj = QOBJECT(qint_from_int(va_arg(*ap, int)));
+    } else if (token_is_escape(token, "%ld")) {
+        obj = QOBJECT(qint_from_int(va_arg(*ap, long)));
+    } else if (token_is_escape(token, "%lld")) {
+        obj = QOBJECT(qint_from_int(va_arg(*ap, long long)));
+    } else if (token_is_escape(token, "%s")) {
+        obj = QOBJECT(qstring_from_str(va_arg(*ap, const char *)));
+    } else if (token_is_escape(token, "%f")) {
+        obj = QOBJECT(qfloat_from_double(va_arg(*ap, double)));
+    } else {
+        goto out;
+    }
+
+    qobject_decref(token);
+    QDECREF(*tokens);
+    *tokens = working;
+
+    return obj;
+
+out:
+    qobject_decref(token);
+    QDECREF(working);
+
+    return NULL;
+}
+
+static QObject *parse_literal(JSONParserContext *ctxt, QList **tokens)
+{
+    QObject *token, *obj;
+    QList *working = qlist_copy(*tokens);
+
+    token = qlist_pop(working);
+    switch (token_get_type(token)) {
+    case JSON_STRING:
+        obj = QOBJECT(qstring_from_escaped_str(ctxt, token));
+        break;
+    case JSON_INTEGER:
+        obj = QOBJECT(qint_from_int(strtoll(token_get_value(token), NULL, 10)));
+        break;
+    case JSON_FLOAT:
+        /* FIXME dependent on locale */
+        obj = QOBJECT(qfloat_from_double(strtod(token_get_value(token), NULL)));
+        break;
+    default:
+        goto out;
+    }
+
+    qobject_decref(token);
+    QDECREF(*tokens);
+    *tokens = working;
+
+    return obj;
+
+out:
+    qobject_decref(token);
+    QDECREF(working);
+
+    return NULL;
+}
+
+static QObject *parse_value(JSONParserContext *ctxt, QList **tokens, va_list *ap)
+{
+    QObject *obj;
+
+    obj = parse_object(ctxt, tokens, ap);
+    if (obj == NULL) {
+        obj = parse_array(ctxt, tokens, ap);
+    }
+    if (obj == NULL) {
+        obj = parse_escape(ctxt, tokens, ap);
+    }
+    if (obj == NULL) {
+        obj = parse_keyword(ctxt, tokens);
+    } 
+    if (obj == NULL) {
+        obj = parse_literal(ctxt, tokens);
+    }
+
+    return obj;
+}
+
+QObject *json_parser_parse(QList *tokens, va_list *ap)
+{
+    JSONParserContext ctxt = {};
+    QList *working = qlist_copy(tokens);
+    QObject *result;
+
+    result = parse_value(&ctxt, &working, ap);
+
+    QDECREF(working);
+
+    return result;
+}
diff --git a/json-parser.h b/json-parser.h
new file mode 100644
index 0000000..97f43f6
--- /dev/null
+++ b/json-parser.h
@@ -0,0 +1,22 @@ 
+/*
+ * JSON Parser 
+ *
+ * Copyright IBM, Corp. 2009
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ *
+ */
+
+#ifndef QEMU_JSON_PARSER_H
+#define QEMU_JSON_PARSER_H
+
+#include "qemu-common.h"
+#include "qlist.h"
+
+QObject *json_parser_parse(QList *tokens, va_list *ap);
+
+#endif