diff --git a/libqblock/libqblock-error.c b/libqblock/libqblock-error.c
index e69de29..2367ab4 100644
--- a/libqblock/libqblock-error.c
+++ b/libqblock/libqblock-error.c
@@ -0,0 +1,49 @@
+/*
+ * QEMU block layer library
+ *
+ * Copyright IBM, Corp. 2013
+ *
+ * Authors:
+ *  Wenchao Xia   <xiawenc@linux.vnet.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ *
+ */
+
+#include "libqblock-error.h"
+#include "libqblock-internal.h"
+
+char *qb_error_get_human_str(QBlockImage *image)
+{
+    char *ret = NULL;
+    QBlockContext *ctx = image->ctx;
+    const char *str;
+    switch (ctx->err_ret) {
+    case QB_ERR_INTERNAL_ERR:
+        str = "Internal error.";
+        break;
+    case QB_ERR_FATAL_ERR:
+        str = "Fatal error.";
+        break;
+    case QB_ERR_INVALID_PARAM:
+        str = "Invalid param.";
+        break;
+    case QB_ERR_BLOCK_OUT_OF_RANGE:
+        str = "request is out of image's range.";
+        break;
+    default:
+        str = "Unknown error.";
+        break;
+    }
+
+    if (ctx->err_ret == QB_ERR_INTERNAL_ERR) {
+        ret = g_strdup_printf("%s %s errno [%d]. strerror [%s].",
+                     str, ctx->g_error->message,
+                     ctx->err_no, strerror(-ctx->err_no));
+    } else {
+        ret = g_strdup_printf("%s %s",
+                     str, ctx->g_error->message);
+    }
+    return ret;
+}
diff --git a/libqblock/libqblock.c b/libqblock/libqblock.c
index e69de29..2283c9e 100644
--- a/libqblock/libqblock.c
+++ b/libqblock/libqblock.c
@@ -0,0 +1,1005 @@
+/*
+ * QEMU block layer library
+ *
+ * Copyright IBM, Corp. 2013
+ *
+ * Authors:
+ *  Wenchao Xia   <xiawenc@linux.vnet.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ *
+ */
+
+#include <unistd.h>
+#include <stdarg.h>
+#include <pthread.h>
+
+#include "libqblock.h"
+#include "libqblock-internal.h"
+
+#include "block/block_int.h"
+
+#define LIBQB_FILENAME_MAX (4096)
+
+typedef struct LibqbFormatStrMapping {
+    const char *fmt_str;
+    QBlockFormat fmt_type;
+} LibqbFormatStrMapping;
+
+static const LibqbFormatStrMapping libqb_formatstr_table[] = {
+    {"cow", QB_FORMAT_COW},
+    {"qed", QB_FORMAT_QED},
+    {"qcow", QB_FORMAT_QCOW},
+    {"qcow2", QB_FORMAT_QCOW2},
+    {"raw", QB_FORMAT_RAW},
+    {"rbd", QB_FORMAT_RBD},
+    {"sheepdog", QB_FORMAT_SHEEPDOG},
+    {"vdi", QB_FORMAT_VDI},
+    {"vmdk", QB_FORMAT_VMDK},
+    {"vpc", QB_FORMAT_VPC},
+};
+
+const char *qb_formattype2str(QBlockFormat fmt_type)
+{
+    int i = 0;
+
+    if ((fmt_type <= QB_FORMAT_NONE) || (fmt_type >= QB_FORMAT_MAX)) {
+        return NULL;
+    }
+    for (i = 0; i < ARRAY_SIZE(libqb_formatstr_table); i++) {
+        if (libqb_formatstr_table[i].fmt_type == fmt_type) {
+            return libqb_formatstr_table[i].fmt_str;
+        }
+    }
+    return NULL;
+}
+
+QBlockFormat qb_str2fmttype(const char *fmt_str)
+{
+    int i = 0;
+
+    if (fmt_str == NULL) {
+        return QB_FORMAT_NONE;
+    }
+    for (i = 0; i < ARRAY_SIZE(libqb_formatstr_table); i++) {
+        if ((strcmp(fmt_str, libqb_formatstr_table[i].fmt_str) == 0)) {
+            return libqb_formatstr_table[i].fmt_type;
+        }
+    }
+    return QB_FORMAT_NONE;
+}
+
+GCC_FMT_ATTR(3, 4)
+static void set_context_err(QBlockContext *context, int err_ret,
+                            const char *fmt, ...)
+{
+    va_list ap;
+
+    if (context->g_error != NULL) {
+        g_error_free(context->g_error);
+    }
+
+    va_start(ap, fmt);
+    context->g_error = g_error_new_valist(qb_error_quark(), err_ret, fmt, ap);
+    va_end(ap);
+
+    context->err_ret = err_ret;
+    if (err_ret == QB_ERR_INTERNAL_ERR) {
+        context->err_no = -errno;
+    } else {
+        context->err_no = 0;
+    }
+}
+
+/*
+ * library init comes here, because block_init() is tagged with flag of
+ * __attribute__((constructor)), and libqblock_init() must be called after it,
+ * so this function was called in create_context() manually instead of tagging.
+ */
+static gpointer libqblock_init(gpointer data)
+{
+    /* Todo: add an assertion about the ABI. */
+    qemu_init_main_loop();
+    bdrv_init();
+    return NULL;
+}
+
+static void create_context(QBlockContext **p_context)
+{
+
+    static GOnce libqblock_init_once = G_ONCE_INIT;
+    g_once(&libqblock_init_once, libqblock_init, NULL);
+
+    *p_context = g_malloc0(sizeof(QBlockContext));
+    /* AIO code could comes here later. */
+}
+
+static void delete_context(QBlockContext **p_context)
+{
+    if ((*p_context)->g_error != NULL) {
+        g_error_free((*p_context)->g_error);
+    }
+    g_free(*p_context);
+    *p_context = NULL;
+}
+
+int qb_image_new(QBlockImage **p_qbi)
+{
+    *p_qbi = g_malloc0_n(1, sizeof(QBlockImage));
+    create_context(&(*p_qbi)->ctx);
+
+    (*p_qbi)->bdrvs = bdrv_new("hda");
+    if ((*p_qbi)->bdrvs == NULL) {
+        set_context_err((*p_qbi)->ctx, QB_ERR_INTERNAL_ERR,
+                       "failed to create the driver.");
+        return QB_ERR_INTERNAL_ERR;
+    }
+    (*p_qbi)->ref_count = 1;
+    return 0;
+}
+
+void qb_image_ref(QBlockImage *qbi)
+{
+    qbi->ref_count++;
+}
+
+void qb_image_unref(QBlockImage **p_qbi)
+{
+    (*p_qbi)->ref_count--;
+    if ((*p_qbi)->ref_count > 0) {
+        return;
+    }
+    delete_context(&(*p_qbi)->ctx);
+    if ((*p_qbi)->filename != NULL) {
+        qb_close(*p_qbi);
+    }
+    if ((*p_qbi)->bdrvs != NULL) {
+        bdrv_delete((*p_qbi)->bdrvs);
+        (*p_qbi)->bdrvs = NULL;
+    }
+    g_free(*p_qbi);
+    *p_qbi = NULL;
+}
+
+/* return 0 if every thing is fine */
+static int loc_check_params(QBlockContext *context,
+                            QBlockLocationInfo *loc)
+{
+    context->err_ret = 0;
+
+    switch (loc->prot_type) {
+    case QB_PROTO_FILE:
+        if (loc->o_file.filename == NULL) {
+            set_context_err(context, QB_ERR_INVALID_PARAM,
+                           "Filename was not set.");
+            goto out;
+        }
+        if (path_has_protocol(loc->o_file.filename) > 0) {
+            set_context_err(context, QB_ERR_INVALID_PARAM,
+                           "filename [%s] had protocol.",
+                           loc->o_file.filename);
+            goto out;
+        }
+        break;
+    default:
+        set_context_err(context, QB_ERR_INVALID_PARAM,
+                       "Protocol type [%d] was not valid.",
+                       loc->prot_type);
+        break;
+    }
+
+ out:
+    return context->err_ret;
+}
+
+/* translate loc structure to internal filename, returned char* need free,
+ * assuming filename is not NULL. *filename would be set to NULL if no valid
+ * filename found. *filename must be freed later.
+ * return 0 if no error with *filename set.
+ */
+static int loc2filename(QBlockContext *context,
+                        QBlockLocationInfo *loc,
+                        char **p_filename)
+{
+    context->err_ret = 0;
+
+    if (*p_filename != NULL) {
+        g_free(*p_filename);
+        *p_filename = NULL;
+    }
+    switch (loc->prot_type) {
+    case QB_PROTO_FILE:
+        *p_filename = g_strdup(loc->o_file.filename);
+        break;
+    default:
+        set_context_err(context, QB_ERR_INVALID_PARAM,
+                 "protocol type [%d] is not supported.",
+                  loc->prot_type);
+        break;
+    }
+
+    return context->err_ret;
+}
+
+/* translate filename to location, loc->prot_type = NONE if fail, filename
+   must be valid. loc internal char pointer must be freed later.
+ * return 0 if no error.
+ */
+static int filename2loc(QBlockContext *context,
+                        QBlockLocationInfo *loc,
+                        const char *filename)
+{
+    context->err_ret = 0;
+
+    if (path_has_protocol(filename) > 0) {
+        set_context_err(context, QB_ERR_INVALID_PARAM,
+                     "Filename [%s] had protocol, not supported now.",
+                     filename);
+        goto out;
+    }
+
+    loc->prot_type = QB_PROTO_FILE;
+    switch (loc->prot_type) {
+    case QB_PROTO_FILE:
+        loc->o_file.filename = g_strdup(filename);
+        break;
+    default:
+        break;
+    }
+
+ out:
+    return context->err_ret;
+}
+
+/* return 0 if OK, or qblock error number */
+static int set_backing_file_options(QBlockContext *context,
+                                    QEMUOptionParameter *param,
+                                    QBlockLocationInfo *loc,
+                                    QBlockFormat *fmt)
+{
+    char *backing_filename = NULL;
+    const char *fmtstr_backing = NULL;
+    int ret = 0;
+
+    if (loc == NULL) {
+        goto out;
+    }
+
+    /* ret can < 0 if loc have not been set, mean user did not specify backing
+       file, so no need to check return value */
+    loc2filename(context, loc, &backing_filename);
+
+    if (backing_filename) {
+        ret = set_option_parameter(param,
+                            BLOCK_OPT_BACKING_FILE, backing_filename);
+        assert(ret == 0);
+        if (fmt == NULL) {
+            goto out;
+        }
+        fmtstr_backing = qb_formattype2str(*fmt);
+        if (fmtstr_backing) {
+            ret = set_option_parameter(param,
+                                BLOCK_OPT_BACKING_FMT, fmtstr_backing);
+            assert(ret == 0);
+        }
+    }
+
+ out:
+    g_free(backing_filename);
+    return ret;
+}
+
+int qb_create(QBlockImage *qbi,
+              QBlockLocationInfo *loc,
+              QBlockFormatInfo *fmt,
+              int flag)
+{
+    int ret = 0, bd_ret;
+    char *filename = NULL;
+    BlockDriverState *bs = NULL;
+    BlockDriver *drv = NULL, *backing_drv = NULL;
+    bool tmp_bool;
+    QBlockContext *context = qbi->ctx;
+
+    const char *fmtstr = NULL, *tmp = NULL;
+    QEMUOptionParameter *param = NULL, *create_options = NULL;
+    QEMUOptionParameter *backing_fmt, *backing_file, *size;
+    QBlockFormatOptionsCOW *o_cow = NULL;
+    QBlockFormatOptionsQED *o_qed = NULL;
+    QBlockFormatOptionsQCOW *o_qcow = NULL;
+    QBlockFormatOptionsQCOW2 *o_qcow2 = NULL;
+    QBlockFormatOptionsRBD *o_rbd = NULL;
+    QBlockFormatOptionsSD *o_sd = NULL;
+    QBlockFormatOptionsVDI *o_vdi = NULL;
+    QBlockFormatOptionsVMDK *o_vmdk = NULL;
+    QBlockFormatOptionsVPC *o_vpc = NULL;
+
+
+    /* check parameters */
+    if (flag & (~LIBQBLOCK_O_VALID_MASK)) {
+        set_context_err(context, QB_ERR_INVALID_PARAM,
+                           "invalid flag was set.");
+        ret = context->err_ret;
+        goto out;
+    }
+
+    if ((loc == NULL) || (qbi == NULL) || (fmt == NULL)) {
+        set_context_err(context, QB_ERR_INVALID_PARAM,
+                          "Got unexpected NULL pointer in parameters.");
+        ret = context->err_ret;
+        goto out;
+    }
+
+    ret = loc_check_params(context, loc);
+    if (ret != 0) {
+        goto out;
+    }
+
+    /* internal translate */
+    ret = loc2filename(context, loc, &filename);
+    if (ret != 0) {
+        goto out;
+    }
+
+    fmtstr = qb_formattype2str(fmt->fmt_type);
+    if (fmtstr == NULL) {
+        set_context_err(context, QB_ERR_INVALID_PARAM,
+                 "Got unexpected NULL pointer in parameters.");
+        ret = context->err_ret;
+        goto out;
+    }
+
+    drv = bdrv_find_format(fmtstr);
+    assert(drv != NULL);
+
+    create_options = append_option_parameters(create_options,
+                                              drv->create_options);
+    param = parse_option_parameters("", create_options, param);
+
+    bd_ret = set_option_parameter_int(param,
+                                BLOCK_OPT_SIZE, fmt->virt_size);
+    assert(bd_ret == 0);
+
+    switch (fmt->fmt_type) {
+    case QB_FORMAT_COW:
+        o_cow = &fmt->o_cow;
+        /* do not need to check loc, it may be not set */
+        ret = set_backing_file_options(context, param,
+                                       &o_cow->backing_loc, NULL);
+        if (ret != 0) {
+            goto out;
+        }
+        break;
+    case QB_FORMAT_QED:
+        o_qed = &fmt->o_qed;
+        ret = set_backing_file_options(context, param,
+                                 &o_qed->backing_loc, &o_qed->backing_fmt);
+        if (ret != 0) {
+            goto out;
+        }
+        bd_ret = set_option_parameter_int(param,
+                                BLOCK_OPT_CLUSTER_SIZE, o_qed->cluster_size);
+        assert(bd_ret == 0);
+        bd_ret = set_option_parameter_int(param,
+                                BLOCK_OPT_TABLE_SIZE, o_qed->table_size);
+        assert(bd_ret == 0);
+        break;
+    case QB_FORMAT_QCOW:
+        o_qcow = &fmt->o_qcow;
+        ret = set_backing_file_options(context, param,
+                                       &o_qcow->backing_loc, NULL);
+        if (ret != 0) {
+            goto out;
+        }
+        tmp = o_qcow->encrypt ? "on" : "off";
+        bd_ret = set_option_parameter(param, BLOCK_OPT_ENCRYPT, tmp);
+        assert(bd_ret == 0);
+        break;
+    case QB_FORMAT_QCOW2:
+        o_qcow2 = &fmt->o_qcow2;
+        ret = set_backing_file_options(context, param,
+                              &o_qcow2->backing_loc, &o_qcow2->backing_fmt);
+        if (ret != 0) {
+            goto out;
+        }
+        tmp = o_qcow2->encrypt ? "on" : "off";
+        bd_ret = set_option_parameter(param, BLOCK_OPT_ENCRYPT, tmp);
+        assert(bd_ret == 0);
+        bd_ret = set_option_parameter_int(param,
+                              BLOCK_OPT_CLUSTER_SIZE, o_qcow2->cluster_size);
+        assert(bd_ret == 0);
+
+        if (o_qcow2->cpt_lv != QB_FORMAT_QCOW2_COMPAT_DEFAULT) {
+            tmp = o_qcow2->cpt_lv == QB_FORMAT_QCOW2_COMPAT_V0_10 ?
+                                     "0.10" : "1.1";
+            bd_ret = set_option_parameter(param,
+                              BLOCK_OPT_COMPAT_LEVEL, tmp);
+            assert(bd_ret == 0);
+        }
+
+        if (o_qcow2->pre_mode != QB_FORMAT_QCOW2_PREALLOC_DEFAULT) {
+            tmp = o_qcow2->pre_mode == QB_FORMAT_QCOW2_PREALLOC_OFF ?
+                                       "off" : "metadata";
+            bd_ret = set_option_parameter(param,
+                              BLOCK_OPT_PREALLOC, tmp);
+            assert(bd_ret == 0);
+        }
+        break;
+
+    case QB_FORMAT_RAW:
+        /* do nothing now. */
+        break;
+    case QB_FORMAT_RBD:
+        o_rbd = &fmt->o_rbd;
+        bd_ret = set_option_parameter_int(param,
+                              BLOCK_OPT_CLUSTER_SIZE, o_rbd->cluster_size);
+        assert(bd_ret == 0);
+        break;
+    case QB_FORMAT_SHEEPDOG:
+        o_sd = &fmt->o_sd;
+        ret = set_backing_file_options(context, param,
+                                       &o_sd->backing_loc, NULL);
+        if (ret != 0) {
+            goto out;
+        }
+        if (o_sd->pre_mode != QB_FORMAT_SD_PREALLOC_DEFAULT) {
+            tmp = o_sd->pre_mode == QB_FORMAT_SD_PREALLOC_OFF ? "off" : "full";
+            bd_ret = set_option_parameter(param,
+                              BLOCK_OPT_PREALLOC, tmp);
+            assert(bd_ret == 0);
+        }
+        break;
+    case QB_FORMAT_VDI:
+        o_vdi = &fmt->o_vdi;
+        /* following option is not always valid depends on configuration */
+        set_option_parameter_int(param,
+                              BLOCK_OPT_CLUSTER_SIZE, o_vdi->cluster_size);
+        if (o_vdi->pre_mode != QB_FORMAT_VDI_PREALLOC_DEFAULT) {
+            tmp_bool = o_vdi->pre_mode == QB_FORMAT_VDI_PREALLOC_METADATA ?
+                                                     true : false;
+            set_option_parameter_int(param, "static", tmp_bool);
+        }
+        break;
+    case QB_FORMAT_VMDK:
+        o_vmdk = &fmt->o_vmdk;
+        ret = set_backing_file_options(context, param,
+                                       &o_vmdk->backing_loc, NULL);
+        if (ret != 0) {
+            goto out;
+        }
+
+        if (o_vmdk->cpt_lv != QB_FORMAT_VMDK_COMPAT_DEFAULT) {
+            tmp_bool = o_vmdk->cpt_lv == QB_FORMAT_VMDK_COMPAT_VMDKV6_TRUE ?
+                                                     true : false;
+            bd_ret = set_option_parameter_int(param, BLOCK_OPT_COMPAT6,
+                                                     tmp_bool);
+            assert(bd_ret == 0);
+        }
+        if (o_vmdk->subfmt != QB_FORMAT_VMDK_SUBFMT_DEFAULT) {
+            switch (o_vmdk->subfmt) {
+            case QB_FORMAT_VMDK_SUBFMT_MONOLITHIC_SPARSE:
+                tmp = "monolithicSparse";
+                break;
+            case QB_FORMAT_VMDK_SUBFMT_MONOLITHIC_FLAT:
+                tmp = "monolithicFlat";
+                break;
+            case QB_FORMAT_VMDK_SUBFMT_TWOGBMAX_EXTENT_SPARSE:
+                tmp = "twoGbMaxExtentSparse";
+                break;
+            case QB_FORMAT_VMDK_SUBFMT_TWOGBMAX_EXTENT_FLAT:
+                tmp = "twoGbMaxExtentFlat";
+                break;
+            case QB_FORMAT_VMDK_SUBFMT_STREAM_OPTIMIZED:
+                tmp = "streamOptimized";
+                break;
+            default:
+                set_context_err(context, QB_ERR_INVALID_PARAM,
+                    "invalid VMDK sumfmt type %d was set.", o_vmdk->subfmt);
+                ret = context->err_ret;
+                goto out;
+                break;
+            }
+            bd_ret = set_option_parameter(param,
+                              BLOCK_OPT_SUBFMT, tmp);
+            assert(bd_ret == 0);
+        }
+        break;
+    case QB_FORMAT_VPC:
+        o_vpc = &fmt->o_vpc;
+        if (o_vpc->subfmt != QB_FORMAT_VPC_SUBFMT_DEFAULT) {
+            tmp = o_vpc->subfmt == QB_FORMAT_VPC_SUBFMT_DYNAMIC ?
+                                               "dynamic" : "fixed";
+            bd_ret = set_option_parameter(param,
+                               BLOCK_OPT_SUBFMT, tmp);
+            assert(bd_ret == 0);
+        }
+        break;
+    default:
+        set_context_err(context, QB_ERR_INVALID_PARAM,
+                        "invalid format type %d was set.", fmt->fmt_type);
+        ret = context->err_ret;
+        goto out;
+        break;
+    }
+
+    backing_file = get_option_parameter(param, BLOCK_OPT_BACKING_FILE);
+    if (backing_file && backing_file->value.s) {
+        if (!strcmp(filename, backing_file->value.s)) {
+            set_context_err(context, QB_ERR_INVALID_PARAM,
+                          "Backing file is the same with new file.");
+            ret = context->err_ret;
+            goto out;
+        }
+    }
+
+    backing_fmt = get_option_parameter(param, BLOCK_OPT_BACKING_FMT);
+    if (backing_fmt && backing_fmt->value.s) {
+        backing_drv = bdrv_find_format(backing_fmt->value.s);
+        assert(backing_drv != NULL);
+    }
+
+    size = get_option_parameter(param, BLOCK_OPT_SIZE);
+    if (size && size->value.n <= 0) {
+        if (backing_file && backing_file->value.s) {
+            uint64_t size;
+            char buf[32];
+            int back_flags;
+
+            /* backing files always opened read-only */
+            back_flags =
+                flag &
+                ~(BDRV_O_RDWR | BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING);
+
+            bs = bdrv_new("");
+
+            ret = bdrv_open(bs, backing_file->value.s,
+                                back_flags, backing_drv);
+            if (ret < 0) {
+                set_context_err(context, QB_ERR_INVALID_PARAM,
+                               "Failed to open the backing file.");
+                ret = context->err_ret;
+                goto out;
+            }
+            bdrv_get_geometry(bs, &size);
+            size *= BDRV_SECTOR_SIZE;
+
+            snprintf(buf, sizeof(buf), "%" PRId64, size);
+            set_option_parameter(param, BLOCK_OPT_SIZE, buf);
+        } else {
+            set_context_err(context, QB_ERR_INTERNAL_ERR,
+                           "Neither size or backing file was not set.");
+            ret = context->err_ret;
+            goto out;
+        }
+    }
+
+    bd_ret = bdrv_create(drv, filename, param);
+
+
+    if (bd_ret < 0) {
+        const char *errstr;
+        if (bd_ret == -ENOTSUP) {
+            errstr = "formatting option not supported.";
+        } else if (bd_ret == -EFBIG) {
+            errstr = "The image size is too large.";
+        } else {
+            errstr = "Error in creating the image.";
+        }
+        set_context_err(context, QB_ERR_INTERNAL_ERR, "%s", errstr);
+        ret = context->err_ret;
+    }
+
+out:
+    free_option_parameters(create_options);
+    free_option_parameters(param);
+    g_free(filename);
+    if (bs) {
+        bdrv_delete(bs);
+    }
+
+    return ret;
+}
+
+int qb_open(QBlockImage *qbi,
+            QBlockLocationInfo *loc,
+            QBlockFormatInfo *fmt,
+            int flag)
+{
+    int ret = 0, bd_ret;
+    BlockDriverState *bs;
+    BlockDriver *bd;
+    const char *fmtstr;
+    char *filename = NULL;
+    QBlockContext *context = qbi->ctx;
+
+    /* take care of user settings */
+    /* do nothing now */
+
+    /* check parameters */
+    if (flag & (~LIBQBLOCK_O_VALID_MASK)) {
+        set_context_err(context, QB_ERR_INVALID_PARAM,
+                      "Invalid flag was set.");
+        ret = context->err_ret;
+        goto out;
+    }
+
+    if ((loc == NULL) || (qbi == NULL)) {
+        set_context_err(context, QB_ERR_INVALID_PARAM,
+                      "Got unexpected NULL pointer in parameters.");
+        ret = context->err_ret;
+        goto out;
+    }
+
+    ret = loc_check_params(context, loc);
+    if (ret != 0) {
+        goto out;
+    }
+
+    /* internal translate */
+    ret = loc2filename(context, loc, &filename);
+    if (ret != 0) {
+        goto out;
+    }
+
+    fmtstr = NULL;
+    bd = NULL;
+    if (fmt != NULL) {
+        fmtstr = qb_formattype2str(fmt->fmt_type);
+    }
+
+    if (fmtstr != NULL) {
+        bd = bdrv_find_format(fmtstr);
+        assert(bd != NULL);
+    }
+
+    /* do real opening */
+    bs = qbi->bdrvs;
+    bd_ret = bdrv_open(bs, filename, flag, bd);
+    if (bd_ret < 0) {
+        set_context_err(context, QB_ERR_INTERNAL_ERR,
+                      "Failed in opening with driver, bd_ret is %d.", bd_ret);
+        ret = context->err_ret;
+        goto out;
+    }
+
+    if (qbi->filename != NULL) {
+        g_free(qbi->filename);
+    }
+    qbi->filename = g_strdup(filename);
+
+ out:
+    g_free(filename);
+    return ret;
+}
+
+void qb_close(QBlockImage *qbi)
+{
+    BlockDriverState *bs;
+
+    bs = qbi->bdrvs;
+
+    if (qbi->filename != NULL) {
+        g_free(qbi->filename);
+        qbi->filename = NULL;
+        bdrv_close(bs);
+    }
+}
+
+int32_t qb_read(QBlockImage *qbi,
+                uint8_t *buf,
+                uint32_t len,
+                uint64_t offset)
+{
+    int bd_ret;
+    BlockDriverState *bs;
+    QBlockContext *context = qbi->ctx;
+
+    context->err_ret = 0;
+    bs = qbi->bdrvs;
+
+    if (len <= 0) {
+        set_context_err(context, QB_ERR_INVALID_PARAM,
+                      "Param len is less or equal to zero.");
+        return context->err_ret;
+    }
+
+    bd_ret = bdrv_pread(bs, offset, buf, len);
+    if (bd_ret < 0) {
+        set_context_err(context, QB_ERR_INTERNAL_ERR,
+                       "I/O errors.");
+        context->err_no = bd_ret;
+        return context->err_ret;
+    }
+
+    return 0;
+}
+
+int32_t qb_write(QBlockImage *qbi,
+                 const uint8_t *buf,
+                 uint32_t len,
+                 uint64_t offset)
+{
+    int bd_ret;
+    BlockDriverState *bs;
+    QBlockContext *context = qbi->ctx;
+
+    context->err_ret = 0;
+    bs = qbi->bdrvs;
+
+    if (len <= 0) {
+        set_context_err(context, QB_ERR_INVALID_PARAM,
+                      "Param len is less or equal to zero.");
+        return context->err_ret;
+    }
+
+    bd_ret = bdrv_pwrite(bs, offset, buf, len);
+    if (bd_ret < 0) {
+        set_context_err(context, QB_ERR_INTERNAL_ERR,
+                       "I/O errors.");
+        context->err_no = bd_ret;
+        return context->err_ret;
+    }
+
+    return 0;
+}
+
+int qb_flush(QBlockImage *qbi)
+{
+    int bd_ret;
+    BlockDriverState *bs;
+    QBlockContext *context = qbi->ctx;
+
+    context->err_ret = 0;
+    bs = qbi->bdrvs;
+    bd_ret = bdrv_flush(bs);
+    if (bd_ret < 0) {
+        set_context_err(context, QB_ERR_INTERNAL_ERR,
+                       "Internal error.");
+    }
+    return context->err_ret;
+}
+
+/*
+ * Assume the length was in range, parameters were valid. Max length is set
+ * to (INT_MAX - 1) << BDRV_SECTOR_BITS, in case of that real_len is bigger
+ * than length.
+ */
+static int qb_check_allocation_in_range(QBlockImage *qbi,
+                                        uint64_t start,
+                                        uint64_t length,
+                                        int *pstatus,
+                                        uint64_t *plength)
+{
+    int ret;
+    int sector_start, sector_num, num;
+    BlockDriverState *bs;
+    unsigned int real_len, ret_len;
+    QBlockContext *context = qbi->ctx;
+
+    context->err_ret = 0;
+    bs = qbi->bdrvs;
+
+    /* translate to sector */
+    sector_start = start >> BDRV_SECTOR_BITS;
+    real_len = (start & (~BDRV_SECTOR_MASK)) + length;
+    sector_num = real_len >> BDRV_SECTOR_BITS;
+    if ((real_len & (~BDRV_SECTOR_MASK)) != 0) {
+        sector_num++;
+    }
+
+    ret = bdrv_is_allocated(bs, sector_start, sector_num, &num);
+    if ((ret == 0) && (num == 0)) {
+        set_context_err(context, QB_ERR_BLOCK_OUT_OF_RANGE,
+                       "Start position was bigger than the image's size.");
+        goto out;
+    }
+
+    *pstatus = ret;
+    ret_len = (num << BDRV_SECTOR_BITS) - (start & (~BDRV_SECTOR_MASK));
+    if (ret_len > length) {
+        ret_len = length;
+    }
+    *plength = ret_len;
+
+ out:
+    return context->err_ret;
+}
+
+int qb_check_allocation(QBlockImage *qbi,
+                        uint64_t start,
+                        uint64_t length,
+                        int *pstatus,
+                        uint64_t *plength)
+{
+    QBlockContext *context = qbi->ctx;
+    int ret = 0;
+
+    context->err_ret = 0;
+    if (length <= 0) {
+        set_context_err(context, QB_ERR_INVALID_PARAM,
+                       "Length is not valid.");
+        goto out;
+    }
+
+    if (qbi->filename == NULL) {
+        set_context_err(context, QB_ERR_INVALID_PARAM,
+                       "Image was not opened first.");
+        goto out;
+    }
+
+    /* Now bdrv_is_allocated take nb_sectors as int with unit sector, but this
+    API take length as uint64_t with unit bytes, so a check is needed to ensure
+    no silent error will happen in translating bytes to sector later if length
+    is too big.
+       Gcc issue? a = (0x7ffffffe << 9) was compiled to 0xfffffffffffffc00, it
+    should be 0xfffffffc00, so use variable instead of direct macro
+    calculation. */
+    uint64_t max_bytes;
+    if (sizeof(int) < (sizeof(uint64_t) - BDRV_SECTOR_BITS/8)) {
+        uint64_t max_sectors = INT_MAX - 1;
+        max_bytes = max_sectors << BDRV_SECTOR_BITS;
+    } else {
+        max_bytes = 0xFFFFFFFFFFFFFFFF;
+    }
+
+    uint64_t remain = length;
+    uint64_t start1 = start, length1, length_ret = 0;
+    int status1 = 0, first_status = 0;
+    bool first_status_got = false;
+    while (remain > 0) {
+        length1 = remain > max_bytes ? max_bytes : remain;
+        ret = qb_check_allocation_in_range(qbi, start1,
+                                           length1, &status1, &length_ret);
+        if (ret != 0) {
+            goto out;
+        }
+
+        if (first_status_got) {
+            if (first_status != status1) {
+                break;
+            }
+        } else {
+            first_status = status1;
+            first_status_got = true;
+        }
+        remain -= length_ret;
+        start1 += length_ret;
+    }
+
+    *pstatus = first_status;
+    *plength = start1 - start;
+
+ out:
+    return context->err_ret;
+}
+
+static void qb_setup_info_addr(const QBlockStaticInfo *info,
+                               QBlockStaticInfoAddr *info_addr)
+{
+    const QBlockLocationInfo *backing_loc = NULL;
+    const bool *encrypt = NULL;
+    const QBlockFormatInfo *fmt = &info->fmt;
+
+    memset(info_addr, 0, sizeof(QBlockStaticInfoAddr));
+
+    switch (fmt->fmt_type) {
+    case QB_FORMAT_COW:
+        backing_loc = &fmt->o_cow.backing_loc;
+        break;
+    case QB_FORMAT_QED:
+        backing_loc = &fmt->o_qed.backing_loc;
+        break;
+    case QB_FORMAT_QCOW:
+        backing_loc = &fmt->o_qcow.backing_loc;
+        encrypt = &fmt->o_qcow.encrypt;
+        break;
+    case QB_FORMAT_QCOW2:
+        backing_loc = &fmt->o_qcow2.backing_loc;
+        encrypt = &fmt->o_qcow2.encrypt;
+        break;
+    case QB_FORMAT_RAW:
+        break;
+    case QB_FORMAT_RBD:
+        break;
+    case QB_FORMAT_SHEEPDOG:
+        backing_loc = &fmt->o_sd.backing_loc;
+        break;
+    case QB_FORMAT_VDI:
+        break;
+    case QB_FORMAT_VMDK:
+        backing_loc = &fmt->o_vmdk.backing_loc;
+        break;
+    case QB_FORMAT_VPC:
+        break;
+    default:
+        break;
+    }
+
+    info_addr->backing_loc = (QBlockLocationInfo *)backing_loc;
+    info_addr->encrypt = (bool *)encrypt;
+}
+
+const uint64_t *qb_get_virt_size(const QBlockStaticInfo *info)
+{
+    return &info->fmt.virt_size;
+}
+
+const QBlockLocationInfo *qb_get_backing_loc(const QBlockStaticInfo *info)
+{
+    QBlockStaticInfoAddr addr;
+    qb_setup_info_addr(info, &addr);
+    return addr.backing_loc;
+}
+
+const bool *qb_get_encrypt(const QBlockStaticInfo *info)
+{
+    QBlockStaticInfoAddr addr;
+    qb_setup_info_addr(info, &addr);
+    return addr.encrypt;
+}
+
+int qb_info_image_static_get(QBlockImage *qbi,
+                             QBlockStaticInfo *info)
+{
+    int ret = 0;
+    BlockDriverState *bs;
+    QBlockStaticInfoAddr addr;
+    const char *fmt_str;
+    uint64_t total_sectors;
+    char backing_filename[LIBQB_FILENAME_MAX];
+    QBlockContext *context = qbi->ctx;
+
+    if (qbi->filename == NULL) {
+        set_context_err(context, QB_ERR_INVALID_PARAM,
+                       "Block Image was not opened.");
+        ret = context->err_ret;
+        goto out;
+    }
+
+    bs = qbi->bdrvs;
+
+    ret = filename2loc(context,
+                       &info->loc,
+                       qbi->filename);
+    if (ret < 0) {
+        goto out;
+    }
+
+    fmt_str = bdrv_get_format_name(bs);
+    info->fmt.fmt_type = qb_str2fmttype(fmt_str);
+    if (info->fmt.fmt_type == QB_FORMAT_NONE) {
+        set_context_err(context, QB_ERR_INVALID_PARAM,
+                       "Image format %s not valid.", fmt_str);
+        ret = context->err_ret;
+        goto out;
+    }
+
+    /* we got the format type and basic location info now, setup the struct
+    pointer to the internal members */
+    qb_setup_info_addr(info, &addr);
+
+    bdrv_get_geometry(bs, &total_sectors);
+    info->fmt.virt_size = total_sectors * BDRV_SECTOR_SIZE;
+
+    if (addr.encrypt != NULL) {
+        *(addr.encrypt) = bdrv_is_encrypted(bs);
+    }
+
+    bdrv_get_full_backing_filename(bs, backing_filename,
+                                   sizeof(backing_filename));
+    if (backing_filename[0] != '\0') {
+        assert(addr.backing_loc != NULL);
+        ret = filename2loc(context,
+                           addr.backing_loc,
+                           backing_filename);
+        if (ret < 0) {
+            goto out;
+        }
+    }
+
+    info->sector_size = BDRV_SECTOR_SIZE;
+
+ out:
+    return ret;
+}
