Patchwork [07/11] Add a lexer for JSON

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Submitter Anthony Liguori
Date Nov. 11, 2009, 5:28 p.m.
Message ID <1257960543-26373-7-git-send-email-aliguori@us.ibm.com>
Download mbox | patch
Permalink /patch/38161/
State New
Headers show

Comments

Anthony Liguori - Nov. 11, 2009, 5:28 p.m.
Our JSON parser is a three stage parser.  The first stage tokenizes the stream
into a set of lexical tokens.  Since the lexical grammar is regular, we can
use a finite state machine to model it.  The state machine will emit tokens
as they are identified.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
---
 Makefile     |    2 +-
 json-lexer.c |  327 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 json-lexer.h |   50 +++++++++
 3 files changed, 378 insertions(+), 1 deletions(-)
 create mode 100644 json-lexer.c
 create mode 100644 json-lexer.h

Patch

diff --git a/Makefile b/Makefile
index 116cd70..e5ab879 100644
--- a/Makefile
+++ b/Makefile
@@ -135,7 +135,7 @@  obj-y += buffered_file.o migration.o migration-tcp.o qemu-sockets.o
 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
+obj-y += qint.o qstring.o qdict.o qlist.o qfloat.o qbool.o json-lexer.o
 obj-y += qemu-config.o
 
 obj-$(CONFIG_BRLAPI) += baum.o
diff --git a/json-lexer.c b/json-lexer.c
new file mode 100644
index 0000000..53697c5
--- /dev/null
+++ b/json-lexer.c
@@ -0,0 +1,327 @@ 
+/*
+ * JSON lexer
+ *
+ * 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 "qstring.h"
+#include "qlist.h"
+#include "qdict.h"
+#include "qint.h"
+#include "qemu-common.h"
+#include "json-lexer.h"
+
+/*
+ * \"([^\\\"]|(\\\"\\'\\\\\\/\\b\\f\\n\\r\\t\\u[0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F]))*\"
+ * '([^\\']|(\\\"\\'\\\\\\/\\b\\f\\n\\r\\t\\u[0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F]))*'
+ * 0|([1-9][0-9]*(.[0-9]+)?([eE]([-+])?[0-9]+))
+ * [{}\[\],:]
+ * [a-z]+
+ *
+ */
+
+enum json_lexer_state {
+    ERROR = 0,
+    IN_DONE_STRING,
+    IN_DQ_UCODE3,
+    IN_DQ_UCODE2,
+    IN_DQ_UCODE1,
+    IN_DQ_UCODE0,
+    IN_DQ_STRING_ESCAPE,
+    IN_DQ_STRING,
+    IN_SQ_UCODE3,
+    IN_SQ_UCODE2,
+    IN_SQ_UCODE1,
+    IN_SQ_UCODE0,
+    IN_SQ_STRING_ESCAPE,
+    IN_SQ_STRING,
+    IN_ZERO,
+    IN_DIGITS,
+    IN_DIGIT,
+    IN_EXP_E,
+    IN_MANTISSA,
+    IN_MANTISSA_DIGITS,
+    IN_NONZERO_NUMBER,
+    IN_NEG_NONZERO_NUMBER,
+    IN_KEYWORD,
+    IN_ESCAPE,
+    IN_ESCAPE_L,
+    IN_ESCAPE_LL,
+    IN_ESCAPE_DONE,
+    IN_WHITESPACE,
+    IN_OPERATOR_DONE,
+    IN_START,
+};
+
+#define TERMINAL(state) [0 ... 0x7F] = (state)
+
+static const uint8_t json_lexer[][256] =  {
+    [IN_DONE_STRING] = {
+        TERMINAL(JSON_STRING),
+    },
+
+    /* double quote string */
+    [IN_DQ_UCODE3] = {
+        ['0' ... '9'] = IN_DQ_STRING,
+        ['a' ... 'f'] = IN_DQ_STRING,
+        ['A' ... 'F'] = IN_DQ_STRING,
+    },
+    [IN_DQ_UCODE2] = {
+        ['0' ... '9'] = IN_DQ_UCODE3,
+        ['a' ... 'f'] = IN_DQ_UCODE3,
+        ['A' ... 'F'] = IN_DQ_UCODE3,
+    },
+    [IN_DQ_UCODE1] = {
+        ['0' ... '9'] = IN_DQ_UCODE2,
+        ['a' ... 'f'] = IN_DQ_UCODE2,
+        ['A' ... 'F'] = IN_DQ_UCODE2,
+    },
+    [IN_DQ_UCODE0] = {
+        ['0' ... '9'] = IN_DQ_UCODE1,
+        ['a' ... 'f'] = IN_DQ_UCODE1,
+        ['A' ... 'F'] = IN_DQ_UCODE1,
+    },
+    [IN_DQ_STRING_ESCAPE] = {
+        ['b'] = IN_DQ_STRING,
+        ['f'] =  IN_DQ_STRING,
+        ['n'] =  IN_DQ_STRING,
+        ['r'] =  IN_DQ_STRING,
+        ['t'] =  IN_DQ_STRING,
+        ['\''] = IN_DQ_STRING,
+        ['\"'] = IN_DQ_STRING,
+        ['u'] = IN_DQ_UCODE0,
+    },
+    [IN_DQ_STRING] = {
+        [1 ... 0xFF] = IN_DQ_STRING,
+        ['\\'] = IN_DQ_STRING_ESCAPE,
+        ['"'] = IN_DONE_STRING,
+    },
+
+    /* single quote string */
+    [IN_SQ_UCODE3] = {
+        ['0' ... '9'] = IN_SQ_STRING,
+        ['a' ... 'f'] = IN_SQ_STRING,
+        ['A' ... 'F'] = IN_SQ_STRING,
+    },
+    [IN_SQ_UCODE2] = {
+        ['0' ... '9'] = IN_SQ_UCODE3,
+        ['a' ... 'f'] = IN_SQ_UCODE3,
+        ['A' ... 'F'] = IN_SQ_UCODE3,
+    },
+    [IN_SQ_UCODE1] = {
+        ['0' ... '9'] = IN_SQ_UCODE2,
+        ['a' ... 'f'] = IN_SQ_UCODE2,
+        ['A' ... 'F'] = IN_SQ_UCODE2,
+    },
+    [IN_SQ_UCODE0] = {
+        ['0' ... '9'] = IN_SQ_UCODE1,
+        ['a' ... 'f'] = IN_SQ_UCODE1,
+        ['A' ... 'F'] = IN_SQ_UCODE1,
+    },
+    [IN_SQ_STRING_ESCAPE] = {
+        ['b'] = IN_SQ_STRING,
+        ['f'] =  IN_SQ_STRING,
+        ['n'] =  IN_SQ_STRING,
+        ['r'] =  IN_SQ_STRING,
+        ['t'] =  IN_SQ_STRING,
+        ['\''] = IN_SQ_STRING,
+        ['\"'] = IN_SQ_STRING,
+        ['u'] = IN_SQ_UCODE0,
+    },
+    [IN_SQ_STRING] = {
+        [1 ... 0xFF] = IN_SQ_STRING,
+        ['\\'] = IN_SQ_STRING_ESCAPE,
+        ['\''] = IN_DONE_STRING,
+    },
+
+    /* Zero */
+    [IN_ZERO] = {
+        TERMINAL(JSON_INTEGER),
+        ['0' ... '9'] = ERROR,
+        ['.'] = IN_MANTISSA,
+    },
+
+    /* Float */
+    [IN_DIGITS] = {
+        TERMINAL(JSON_FLOAT),
+        ['0' ... '9'] = IN_DIGITS,
+    },
+
+    [IN_DIGIT] = {
+        ['0' ... '9'] = IN_DIGITS,
+    },
+
+    [IN_EXP_E] = {
+        ['-'] = IN_DIGIT,
+        ['+'] = IN_DIGIT,
+        ['0' ... '9'] = IN_DIGITS,
+    },
+
+    [IN_MANTISSA_DIGITS] = {
+        TERMINAL(JSON_FLOAT),
+        ['0' ... '9'] = IN_MANTISSA_DIGITS,
+        ['e'] = IN_EXP_E,
+        ['E'] = IN_EXP_E,
+    },
+
+    [IN_MANTISSA] = {
+        ['0' ... '9'] = IN_MANTISSA_DIGITS,
+    },
+
+    /* Number */
+    [IN_NONZERO_NUMBER] = {
+        TERMINAL(JSON_INTEGER),
+        ['0' ... '9'] = IN_NONZERO_NUMBER,
+        ['e'] = IN_EXP_E,
+        ['E'] = IN_EXP_E,
+        ['.'] = IN_MANTISSA,
+    },
+
+    [IN_NEG_NONZERO_NUMBER] = {
+        ['0'] = IN_ZERO,
+        ['1' ... '9'] = IN_NONZERO_NUMBER,
+    },
+
+    /* keywords */
+    [IN_KEYWORD] = {
+        TERMINAL(JSON_KEYWORD),
+        ['a' ... 'z'] = IN_KEYWORD,
+    },
+
+    /* whitespace */
+    [IN_WHITESPACE] = {
+        TERMINAL(JSON_SKIP),
+        [' '] = IN_WHITESPACE,
+        ['\t'] = IN_WHITESPACE,
+        ['\r'] = IN_WHITESPACE,
+        ['\n'] = IN_WHITESPACE,
+    },        
+
+    /* operator */
+    [IN_OPERATOR_DONE] = {
+        TERMINAL(JSON_OPERATOR),
+    },
+
+    /* escape */
+    [IN_ESCAPE_DONE] = {
+        TERMINAL(JSON_ESCAPE),
+    },
+
+    [IN_ESCAPE_LL] = {
+        ['d'] = IN_ESCAPE_DONE,
+    },
+
+    [IN_ESCAPE_L] = {
+        ['d'] = IN_ESCAPE_DONE,
+        ['l'] = IN_ESCAPE_LL,
+    },
+
+    [IN_ESCAPE] = {
+        ['d'] = IN_ESCAPE_DONE,
+        ['i'] = IN_ESCAPE_DONE,
+        ['p'] = IN_ESCAPE_DONE,
+        ['s'] = IN_ESCAPE_DONE,
+        ['f'] = IN_ESCAPE_DONE,
+        ['l'] = IN_ESCAPE_L,
+    },
+
+    /* top level rule */
+    [IN_START] = {
+        ['"'] = IN_DQ_STRING,
+        ['\''] = IN_SQ_STRING,
+        ['0'] = IN_ZERO,
+        ['1' ... '9'] = IN_NONZERO_NUMBER,
+        ['-'] = IN_NEG_NONZERO_NUMBER,
+        ['{'] = IN_OPERATOR_DONE,
+        ['}'] = IN_OPERATOR_DONE,
+        ['['] = IN_OPERATOR_DONE,
+        [']'] = IN_OPERATOR_DONE,
+        [','] = IN_OPERATOR_DONE,
+        [':'] = IN_OPERATOR_DONE,
+        ['a' ... 'z'] = IN_KEYWORD,
+        ['%'] = IN_ESCAPE,
+        [' '] = IN_WHITESPACE,
+        ['\t'] = IN_WHITESPACE,
+        ['\r'] = IN_WHITESPACE,
+        ['\n'] = IN_WHITESPACE,
+    },
+};
+
+void json_lexer_init(JSONLexer *lexer, JSONLexerEmitter func)
+{
+    lexer->emit = func;
+    lexer->state = IN_START;
+    lexer->token = qstring_new();
+}
+
+static int json_lexer_feed_char(JSONLexer *lexer, char ch)
+{
+    char buf[2];
+
+    lexer->x++;
+    if (ch == '\n') {
+        lexer->x = 0;
+        lexer->y++;
+    }
+
+    lexer->state = json_lexer[lexer->state][(uint8_t)ch];
+
+    switch (lexer->state) {
+    case JSON_OPERATOR:
+    case JSON_ESCAPE:
+    case JSON_INTEGER:
+    case JSON_FLOAT:
+    case JSON_KEYWORD:
+    case JSON_STRING:
+        lexer->emit(lexer, lexer->token, lexer->state, lexer->x, lexer->y);
+    case JSON_SKIP:
+        lexer->state = json_lexer[IN_START][(uint8_t)ch];
+        QDECREF(lexer->token);
+        lexer->token = qstring_new();
+        break;
+    case ERROR:
+        return -EINVAL;
+    default:
+        break;
+    }
+
+    buf[0] = ch;
+    buf[1] = 0;
+
+    qstring_append(lexer->token, buf);
+
+    return 0;
+}
+
+int json_lexer_feed(JSONLexer *lexer, const char *buffer, size_t size)
+{
+    size_t i;
+
+    for (i = 0; i < size; i++) {
+        int err;
+
+        err = json_lexer_feed_char(lexer, buffer[i]);
+        if (err < 0) {
+            return err;
+        }
+    }
+
+    return 0;
+}
+
+int json_lexer_flush(JSONLexer *lexer)
+{
+    return json_lexer_feed_char(lexer, 0);
+}
+
+void json_lexer_destroy(JSONLexer *lexer)
+{
+    QDECREF(lexer->token);
+}
diff --git a/json-lexer.h b/json-lexer.h
new file mode 100644
index 0000000..3b50c46
--- /dev/null
+++ b/json-lexer.h
@@ -0,0 +1,50 @@ 
+/*
+ * JSON lexer
+ *
+ * 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_LEXER_H
+#define QEMU_JSON_LEXER_H
+
+#include "qstring.h"
+#include "qlist.h"
+
+typedef enum json_token_type {
+    JSON_OPERATOR = 100,
+    JSON_INTEGER,
+    JSON_FLOAT,
+    JSON_KEYWORD,
+    JSON_STRING,
+    JSON_ESCAPE,
+    JSON_SKIP,
+} JSONTokenType;
+
+typedef struct JSONLexer JSONLexer;
+
+typedef void (JSONLexerEmitter)(JSONLexer *, QString *, JSONTokenType, int x, int y);
+
+struct JSONLexer
+{
+    JSONLexerEmitter *emit;
+    int state;
+    QString *token;
+    int x, y;
+};
+
+void json_lexer_init(JSONLexer *lexer, JSONLexerEmitter func);
+
+int json_lexer_feed(JSONLexer *lexer, const char *buffer, size_t size);
+
+int json_lexer_flush(JSONLexer *lexer);
+
+void json_lexer_destroy(JSONLexer *lexer);
+
+#endif