This page gives an overview of various categories of utility functions that we use in Kaldi code.
In text-utils.h are various functions for manipulating strings, mostly used in parsing. Important ones include the templated function ConvertStringToInteger(), and the overloaded ConvertStringToReal() functions which are defined for float and double. There is also the SplitStringToIntegers() template whose output is a vector of integers, and SplitStringToVector() which splits a string into a vector of strings.
In stl-utils.h are templated functions for manipulating STL types. A commonly used one is SortAndUniq(), which sorts and removes duplicates from a vector (of an arbitrary type). The function CopySetToVector() copies the elements of a set into a vector, and is part of a larger category of similar functions that move data between sets, vectors and maps (see a list in stl-utils.h). There are also the hashing-function types VectorHasher (for vectors of integers) and StringHasher (for strings); these are for use with the STL unordered_map and unordered_set templates. Another commonly used function is DeletePointers(), which deletes pointers in a std::vector of pointers, and sets them to NULL.
In kaldi-math.h, apart from a number of standard #defines which are provided in case they are not in the system header math.h, there are some math utility functions. These include most importantly:
In const-integer-set.h is a class ConstIntegerSet that stores a set of integers in an efficient way and allows fast querying. The caveat is that the set cannot be changed after initializing the object. This is used e.g. in decision-tree code. Depending on the value of the integers in the set, it may store them internally as vector<bool> or as a sorted vector of integers.
Other utility-type functions and classes are in simple-io-funcs.h and hash-list.h, but these have more specialized uses. Some additional utility functions and macros, mostly quite specialized, that the matrix code depends on, are in kaldi-utils.h; these include things like byte swapping, memory alignment, and mechanisms for compile-time assertions (useful in templates).