Resource management (computing): Difference between revisions

Revision as of 21:29, 8 December 2018

Revision as of 16:21, 30 November 2019

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The basic approach to resource management is to acquire a resource, do something with it, then release it, yielding code of the form (illustrated with opening a file in Python):

<source lang=python>

def work_with_file(filename: str):

f = open(filename)

...

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The resource leak can be resolved in languages that support a <code>finally</code> construction (like Python) by placing the body in a <code>try</code> clause, and the release in a <code>finally</code> clause:

<source lang=python>

def work_with_file(filename: str):

f = open(filename)

try:

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This ensures correct release even if there is a return within the body or an exception thrown. Further, note that the acquisition occurs ''before'' the <code>try</code> clause, ensuring that the <code>finally</code> clause is only executed if the <code>open</code> code succeeds (without throwing an exception), assuming that "no exception" means "success" (as is the case for <code>open</code> in Python). If resource acquisition can fail without throwing an exception, such as by returning a form of <code>null</code>, it must also be checked before release, such as:

<source lang=python>

def work_with_file(filename: str):

f = open(filename)

try:

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While this ensures correct resource management, it fails to provide adjacency or encapsulation. In many languages there are mechanisms that provide encapsulation, such as the <code>with</code> statement in Python:

<source lang=python>

def work_with_file(filename: str):

with open(filename) as f:

...