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Preface

When we use go for data serialization or deserialization, we may often involve string and byte array conversions. For example:

If str, err: = json.Marshal (from); err! = nil {panic (err)} else {return string (str)}

Json is serialized to the [] byte type, which needs to be converted to a string type. When the amount of data is small, the overhead of conversion between types is negligible, but when the amount of data increases, it may become a performance bottleneck. Using efficient conversion methods can reduce this overhead.

Data structure

Before you know how to transform it, you need to understand its underlying data structure.

This article is based on go 1.13.12

String:

Type stringStruct struct {str unsafe.Pointer len int}

Slice:

Type slice struct {array unsafe.Pointer len int cap int}

Compared to the structure of slice, string lacks a cap field that represents capacity, so you can't use the built-in cap () function for string traversal, so why doesn't string need the cap field? Because string in go is designed as an immutable type (and, of course, in many other languages), because it cannot append elements like slice, it does not need the cap field to determine whether it exceeds the capacity of the underlying array to decide whether to expand.

Only the len attribute does not affect read operations such as for-range, because the for-range operation only decides whether to jump out of the loop based on the len

So why is the string set to immutable? Because this ensures that the underlying array of the string does not change.

For example, map uses string as the key, and if the underlying character array changes, the calculated hash value will also change, so that the previous value can not be found when positioning from map, so its immutable property avoids this situation, and string is also suitable as a key for map. In addition, immutability can also ensure the thread safety of data.

Conventional implementation

String immutability has many advantages, and in order to maintain its immutability, string and byte array interconversion is generally achieved by copying data:

Var a string = "hello world" var b [] byte = [] byte (a) / / string to [] bytea = string (b) / / [] byte to string

This approach is simple to implement, but is implemented through underlying data replication, which is converted to function calls to slicebytetostring and stringtoslicebyte respectively during compilation.

String to [] byte

Func stringtoslicebyte (buf * tmpBuf, s string) [] byte {var b [] byte if buf! = nil & & len (s)

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