StrDiffSynch 2.1.0

One of two strings can change into the other when absorbing the difference among them. Remote strings could be synchronized through minimum data.

StrDiff

One of two strings can change into the other when absorbing the difference among them.

import json
from StrDiffSynch import StrDiff

data1 = json.dumps({"name": "davis", "other": {"age": 18}})
data2 = json.dumps({"name": "davis", "age": 18})
diff = StrDiff(data1, data2)
assert data1 + diff == data2
assert diff + data1 == data2

SynchBox

This class is used for synchronizing big string but not big enough to have to be stored in a database, among two endpoints.

import asyncio

from StrDiffSynch import SynchBox

# LOCAL
# Define a SynchBox instance to contain the string
synch_box = SynchBox('This is big data.')
# update the containing string
synch_box.local_str = 'This is another big data.'
# If a request with the remote string hash value comes to ask to synchronize the string at the remote endpoint, local endpoint handles the request.
# REMOTE
synch_box2 = SynchBox('')
remote_str_hash = synch_box2.local_str_hash
# request though the web
# LOCAL
remote_synch_data = synch_box.handle_remote_synch_command(remote_str_hash)
# response through the web
# REMOTE
# Because no synchronization has happened, remote_synch_data would be the raw big string, 'This is another big data.' as demonstration.
synch_box2.handle_local_synch_command(remote_synch_data)
assert 'This is another big data.' == remote_synch_data == synch_box2.local_str

# Now repeat
# REMOTE
remote_str_hash = synch_box2.local_str_hash
# request though the web
# LOCAL
remote_synch_data = synch_box.handle_remote_synch_command(remote_str_hash)
# response through the web
# REMOTE
# Well now that initial synchronization has happened, SynchBox will try to find the difference information between these two copy , which is usually much smaller than the raw string.
assert type(remote_synch_data) != str and any(['h' == i[0] for i in remote_synch_data])
synch_box2.handle_local_synch_command(remote_synch_data)  # At this step,there is nothing to change in fact.
assert synch_box2.local_str == synch_box.local_str

# Now repeat
# LOCAL
# make some change
synch_box.local_str += 'u28dy2'
# REMOTE
remote_str_hash = synch_box2.local_str_hash
# request though the web
# LOCAL
remote_synch_data = synch_box.handle_remote_synch_command(remote_str_hash)
# response through the web
# REMOTE
assert type(remote_synch_data) != str and any(['h' == i[0] for i in remote_synch_data])
old_str = synch_box2.local_str
synch_box2.handle_local_synch_command(remote_synch_data)  # At this step,changes happen.
assert synch_box2.local_str == synch_box.local_str != old_str

# Now repeat
# Vice versa, REMOTE could synchronizes LOCAL.
# REMOTE
# make some change
synch_box2.local_str = synch_box2.local_str[0:3] + synch_box2.local_str[-3:]
# LOCAL
str_hash = synch_box.local_str_hash
# request though the web
# REMOTE
synch_data = synch_box2.handle_remote_synch_command(str_hash)
# response through the web
# LOCAL
assert type(synch_data) != str and any(['h' == i[0] for i in synch_data])
old_str = synch_box.local_str
synch_box.handle_local_synch_command(synch_data)  # At this step,changes happen.
assert synch_box2.local_str == synch_box.local_str != old_str

# A bad situation
# REMOTE
remote_str_hash = synch_box2.local_str_hash
# request though the web
# LOCAL
remote_synch_data = synch_box.handle_remote_synch_command(remote_str_hash)
# response through the web
# REMOTE
assert type(remote_synch_data) != str and any(['h' == i[0] for i in remote_synch_data])
# Before the difference information synchronization data comes, the string with the hash value remote_str_hash changes for some reason.
synch_box2.local_str = 'Hello world'
# The coming information can't be handled.
try:
    synch_box2.handle_local_synch_command(remote_synch_data)
except AssertionError:
    print('Fail to handle_local_synch_command')


# If you want to automatically handle this bad situation, you can pass the keyword parameter strdiff_add_error_handler to handle_local_synch_command, to be called to fetch the raw string.
# For example,
# def fetch_raw_string():
#     return requests.get('http://www.baidu.com/raw-string')
# We will demonstrate easily.
def fetch_raw_string():
    return synch_box.local_str


synch_box2.handle_local_synch_command(remote_synch_data, fetch_raw_string)  # At this step,changes happen
assert synch_box2.local_str == synch_box.local_str


# If you are using this module in a coroutine function, to request you can pass a coroutine function as the error handler,
# for example:
# async def fetch_raw_string():
#     async with aiohttp.ClientSession().get('http://www.baidu.com/raw-string') as r:
#         return await r.text()
# We will demonstrate easily.
async def fetch_raw_string():
    return synch_box.local_str


async def main():
    handle_local_synch_command_res = synch_box2.handle_local_synch_command(remote_synch_data, fetch_raw_string)
    # try to await the result only when necessary.
    if type(handle_local_synch_command_res) == asyncio.Task:
        await handle_local_synch_command_res
    assert synch_box2.local_str == synch_box.local_str


asyncio.get_event_loop().run_until_complete(main())