import

qemu/qobject/json-parser.c

@@ -0,0 +1,713 @@
+/*
+ * 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 <stdarg.h>
+
+#include "qemu-common.h"
+#include "qapi/qmp/qstring.h"
+#include "qapi/qmp/qint.h"
+#include "qapi/qmp/qdict.h"
+#include "qapi/qmp/qlist.h"
+#include "qapi/qmp/qfloat.h"
+#include "qapi/qmp/qbool.h"
+#include "qapi/qmp/json-parser.h"
+#include "qapi/qmp/json-lexer.h"
+#include "qapi/qmp/qerror.h"
+
+typedef struct JSONParserContext
+{
+    Error *err;
+    struct {
+        QObject **buf;
+        size_t pos;
+        size_t count;
+    } tokens;
+} 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, 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 GCC_FMT_ATTR(3, 4) parse_error(JSONParserContext *ctxt,
+                                           QObject *token, const char *msg, ...)
+{
+    va_list ap;
+    char message[1024];
+    va_start(ap, msg);
+    vsnprintf(message, sizeof(message), msg, ap);
+    va_end(ap);
+    if (ctxt->err) {
+        error_free(ctxt->err);
+        ctxt->err = NULL;
+    }
+    error_setg(&ctxt->err, "JSON parse error, %s", message);
+}
+
+/**
+ * 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 'f':
+                qstring_append(str, "\f");
+                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);
+        }
+    }
+
+    return str;
+
+out:
+    QDECREF(str);
+    return NULL;
+}
+
+static QObject *parser_context_pop_token(JSONParserContext *ctxt)
+{
+    QObject *token;
+    g_assert(ctxt->tokens.pos < ctxt->tokens.count);
+    token = ctxt->tokens.buf[ctxt->tokens.pos];
+    ctxt->tokens.pos++;
+    return token;
+}
+
+/* Note: parser_context_{peek|pop}_token do not increment the
+ * token object's refcount. In both cases the references will continue
+ * to be tracked and cleaned up in parser_context_free(), so do not
+ * attempt to free the token object.
+ */
+static QObject *parser_context_peek_token(JSONParserContext *ctxt)
+{
+    QObject *token;
+    g_assert(ctxt->tokens.pos < ctxt->tokens.count);
+    token = ctxt->tokens.buf[ctxt->tokens.pos];
+    return token;
+}
+
+static JSONParserContext parser_context_save(JSONParserContext *ctxt)
+{
+    JSONParserContext saved_ctxt = {0};
+    saved_ctxt.tokens.pos = ctxt->tokens.pos;
+    saved_ctxt.tokens.count = ctxt->tokens.count;
+    saved_ctxt.tokens.buf = ctxt->tokens.buf;
+    return saved_ctxt;
+}
+
+static void parser_context_restore(JSONParserContext *ctxt,
+                                   JSONParserContext saved_ctxt)
+{
+    ctxt->tokens.pos = saved_ctxt.tokens.pos;
+    ctxt->tokens.count = saved_ctxt.tokens.count;
+    ctxt->tokens.buf = saved_ctxt.tokens.buf;
+}
+
+static void tokens_append_from_iter(QObject *obj, void *opaque)
+{
+    JSONParserContext *ctxt = opaque;
+    g_assert(ctxt->tokens.pos < ctxt->tokens.count);
+    ctxt->tokens.buf[ctxt->tokens.pos++] = obj;
+    qobject_incref(obj);
+}
+
+static JSONParserContext *parser_context_new(QList *tokens)
+{
+    JSONParserContext *ctxt;
+    size_t count;
+
+    if (!tokens) {
+        return NULL;
+    }
+
+    count = qlist_size(tokens);
+    if (count == 0) {
+        return NULL;
+    }
+
+    ctxt = g_malloc0(sizeof(JSONParserContext));
+    ctxt->tokens.pos = 0;
+    ctxt->tokens.count = count;
+    ctxt->tokens.buf = g_malloc(count * sizeof(QObject *));
+    qlist_iter(tokens, tokens_append_from_iter, ctxt);
+    ctxt->tokens.pos = 0;
+
+    return ctxt;
+}
+
+/* to support error propagation, ctxt->err must be freed separately */
+static void parser_context_free(JSONParserContext *ctxt)
+{
+    int i;
+    if (ctxt) {
+        for (i = 0; i < ctxt->tokens.count; i++) {
+            qobject_decref(ctxt->tokens.buf[i]);
+        }
+        g_free(ctxt->tokens.buf);
+        g_free(ctxt);
+    }
+}
+
+/**
+ * Parsing rules
+ */
+static int parse_pair(JSONParserContext *ctxt, QDict *dict, va_list *ap)
+{
+    QObject *key = NULL, *token = NULL, *value, *peek;
+    JSONParserContext saved_ctxt = parser_context_save(ctxt);
+
+    peek = parser_context_peek_token(ctxt);
+    if (peek == NULL) {
+        parse_error(ctxt, NULL, "premature EOI");
+        goto out;
+    }
+
+    key = parse_value(ctxt, ap);
+    if (!key || qobject_type(key) != QTYPE_QSTRING) {
+        parse_error(ctxt, peek, "key is not a string in object");
+        goto out;
+    }
+
+    token = parser_context_pop_token(ctxt);
+    if (token == NULL) {
+        parse_error(ctxt, NULL, "premature EOI");
+        goto out;
+    }
+
+    if (!token_is_operator(token, ':')) {
+        parse_error(ctxt, token, "missing : in object pair");
+        goto out;
+    }
+
+    value = parse_value(ctxt, 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(key);
+
+    return 0;
+
+out:
+    parser_context_restore(ctxt, saved_ctxt);
+    qobject_decref(key);
+
+    return -1;
+}
+
+static QObject *parse_object(JSONParserContext *ctxt, va_list *ap)
+{
+    QDict *dict = NULL;
+    QObject *token, *peek;
+    JSONParserContext saved_ctxt = parser_context_save(ctxt);
+
+    token = parser_context_pop_token(ctxt);
+    if (token == NULL) {
+        goto out;
+    }
+
+    if (!token_is_operator(token, '{')) {
+        goto out;
+    }
+
+    dict = qdict_new();
+
+    peek = parser_context_peek_token(ctxt);
+    if (peek == NULL) {
+        parse_error(ctxt, NULL, "premature EOI");
+        goto out;
+    }
+
+    if (!token_is_operator(peek, '}')) {
+        if (parse_pair(ctxt, dict, ap) == -1) {
+            goto out;
+        }
+
+        token = parser_context_pop_token(ctxt);
+        if (token == NULL) {
+            parse_error(ctxt, NULL, "premature EOI");
+            goto out;
+        }
+
+        while (!token_is_operator(token, '}')) {
+            if (!token_is_operator(token, ',')) {
+                parse_error(ctxt, token, "expected separator in dict");
+                goto out;
+            }
+
+            if (parse_pair(ctxt, dict, ap) == -1) {
+                goto out;
+            }
+
+            token = parser_context_pop_token(ctxt);
+            if (token == NULL) {
+                parse_error(ctxt, NULL, "premature EOI");
+                goto out;
+            }
+        }
+    } else {
+        (void)parser_context_pop_token(ctxt);
+    }
+
+    return QOBJECT(dict);
+
+out:
+    parser_context_restore(ctxt, saved_ctxt);
+    QDECREF(dict);
+    return NULL;
+}
+
+static QObject *parse_array(JSONParserContext *ctxt, va_list *ap)
+{
+    QList *list = NULL;
+    QObject *token, *peek;
+    JSONParserContext saved_ctxt = parser_context_save(ctxt);
+
+    token = parser_context_pop_token(ctxt);
+    if (token == NULL) {
+        goto out;
+    }
+
+    if (!token_is_operator(token, '[')) {
+        goto out;
+    }
+
+    list = qlist_new();
+
+    peek = parser_context_peek_token(ctxt);
+    if (peek == NULL) {
+        parse_error(ctxt, NULL, "premature EOI");
+        goto out;
+    }
+
+    if (!token_is_operator(peek, ']')) {
+        QObject *obj;
+
+        obj = parse_value(ctxt, ap);
+        if (obj == NULL) {
+            parse_error(ctxt, token, "expecting value");
+            goto out;
+        }
+
+        qlist_append_obj(list, obj);
+
+        token = parser_context_pop_token(ctxt);
+        if (token == NULL) {
+            parse_error(ctxt, NULL, "premature EOI");
+            goto out;
+        }
+
+        while (!token_is_operator(token, ']')) {
+            if (!token_is_operator(token, ',')) {
+                parse_error(ctxt, token, "expected separator in list");
+                goto out;
+            }
+
+            obj = parse_value(ctxt, ap);
+            if (obj == NULL) {
+                parse_error(ctxt, token, "expecting value");
+                goto out;
+            }
+
+            qlist_append_obj(list, obj);
+
+            token = parser_context_pop_token(ctxt);
+            if (token == NULL) {
+                parse_error(ctxt, NULL, "premature EOI");
+                goto out;
+            }
+        }
+    } else {
+        (void)parser_context_pop_token(ctxt);
+    }
+
+    return QOBJECT(list);
+
+out:
+    parser_context_restore(ctxt, saved_ctxt);
+    QDECREF(list);
+    return NULL;
+}
+
+static QObject *parse_keyword(JSONParserContext *ctxt)
+{
+    QObject *token, *ret;
+    JSONParserContext saved_ctxt = parser_context_save(ctxt);
+
+    token = parser_context_pop_token(ctxt);
+    if (token == NULL) {
+        goto out;
+    }
+
+    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;
+    }
+
+    return ret;
+
+out: 
+    parser_context_restore(ctxt, saved_ctxt);
+
+    return NULL;
+}
+
+static QObject *parse_escape(JSONParserContext *ctxt, va_list *ap)
+{
+    QObject *token = NULL, *obj;
+    JSONParserContext saved_ctxt = parser_context_save(ctxt);
+
+    if (ap == NULL) {
+        goto out;
+    }
+
+    token = parser_context_pop_token(ctxt);
+    if (token == NULL) {
+        goto out;
+    }
+
+    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") ||
+               token_is_escape(token, "%I64d")) {
+        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;
+    }
+
+    return obj;
+
+out:
+    parser_context_restore(ctxt, saved_ctxt);
+
+    return NULL;
+}
+
+static QObject *parse_literal(JSONParserContext *ctxt)
+{
+    QObject *token, *obj;
+    JSONParserContext saved_ctxt = parser_context_save(ctxt);
+
+    token = parser_context_pop_token(ctxt);
+    if (token == NULL) {
+        goto out;
+    }
+
+    switch (token_get_type(token)) {
+    case JSON_STRING:
+        obj = QOBJECT(qstring_from_escaped_str(ctxt, token));
+        break;
+    case JSON_INTEGER: {
+        /* A possibility exists that this is a whole-valued float where the
+         * fractional part was left out due to being 0 (.0). It's not a big
+         * deal to treat these as ints in the parser, so long as users of the
+         * resulting QObject know to expect a QInt in place of a QFloat in
+         * cases like these.
+         *
+         * However, in some cases these values will overflow/underflow a
+         * QInt/int64 container, thus we should assume these are to be handled
+         * as QFloats/doubles rather than silently changing their values.
+         *
+         * strtoll() indicates these instances by setting errno to ERANGE
+         */
+        int64_t value;
+
+        errno = 0; /* strtoll doesn't set errno on success */
+        value = strtoll(token_get_value(token), NULL, 10);
+        if (errno != ERANGE) {
+            obj = QOBJECT(qint_from_int(value));
+            break;
+        }
+        /* fall through to JSON_FLOAT */
+    }
+    case JSON_FLOAT:
+        /* FIXME dependent on locale */
+        obj = QOBJECT(qfloat_from_double(strtod(token_get_value(token), NULL)));
+        break;
+    default:
+        goto out;
+    }
+
+    return obj;
+
+out:
+    parser_context_restore(ctxt, saved_ctxt);
+
+    return NULL;
+}
+
+static QObject *parse_value(JSONParserContext *ctxt, va_list *ap)
+{
+    QObject *obj;
+
+    obj = parse_object(ctxt, ap);
+    if (obj == NULL) {
+        obj = parse_array(ctxt, ap);
+    }
+    if (obj == NULL) {
+        obj = parse_escape(ctxt, ap);
+    }
+    if (obj == NULL) {
+        obj = parse_keyword(ctxt);
+    } 
+    if (obj == NULL) {
+        obj = parse_literal(ctxt);
+    }
+
+    return obj;
+}
+
+QObject *json_parser_parse(QList *tokens, va_list *ap)
+{
+    return json_parser_parse_err(tokens, ap, NULL);
+}
+
+QObject *json_parser_parse_err(QList *tokens, va_list *ap, Error **errp)
+{
+    JSONParserContext *ctxt = parser_context_new(tokens);
+    QObject *result;
+
+    if (!ctxt) {
+        return NULL;
+    }
+
+    result = parse_value(ctxt, ap);
+
+    error_propagate(errp, ctxt->err);
+
+    parser_context_free(ctxt);
+
+    return result;
+}