98 lines
3.8 KiB
C
98 lines
3.8 KiB
C
/*
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* psql - the PostgreSQL interactive terminal
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*
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* Copyright (c) 2000-2024, PostgreSQL Global Development Group
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*
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* This implements a sort of variable repository. One could also think of it
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* as a cheap version of an associative array. Each variable has a string
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* name and a string value. The value can't be NULL, or more precisely
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* that's not distinguishable from the variable being unset.
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*
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* src/bin/psql/variables.h
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*/
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#ifndef VARIABLES_H
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#define VARIABLES_H
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/*
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* Variables can be given "assign hook" functions. The assign hook can
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* prevent invalid values from being assigned, and can update internal C
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* variables to keep them in sync with the variable's current value.
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*
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* An assign hook function is called before any attempted assignment, with the
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* proposed new value of the variable (or with NULL, if an \unset is being
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* attempted). If it returns false, the assignment doesn't occur --- it
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* should print an error message with pg_log_error() to tell the user why.
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*
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* When an assign hook function is installed with SetVariableHooks(), it is
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* called with the variable's current value (or with NULL, if it wasn't set
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* yet). But its return value is ignored in this case. The hook should be
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* set before any possibly-invalid value can be assigned.
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*/
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typedef bool (*VariableAssignHook) (const char *newval);
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/*
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* Variables can also be given "substitute hook" functions. The substitute
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* hook can replace values (including NULL) with other values, allowing
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* normalization of variable contents. For example, for a boolean variable,
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* we wish to interpret "\unset FOO" as "\set FOO off", and we can do that
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* by installing a substitute hook. (We can use the same substitute hook
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* for all bool or nearly-bool variables, which is why this responsibility
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* isn't part of the assign hook.)
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*
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* The substitute hook is called before any attempted assignment, and before
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* the assign hook if any, passing the proposed new value of the variable as a
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* malloc'd string (or NULL, if an \unset is being attempted). It can return
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* the same value, or a different malloc'd string, or modify the string
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* in-place. It should free the passed-in value if it's not returning it.
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* The substitute hook generally should not complain about erroneous values;
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* that's a job for the assign hook.
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*
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* When a substitute hook is installed with SetVariableHooks(), it is applied
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* to the variable's current value (typically NULL, if it wasn't set yet).
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* That also happens before applying the assign hook.
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*/
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typedef char *(*VariableSubstituteHook) (char *newval);
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/*
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* Data structure representing one variable.
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*
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* Note: if value == NULL then the variable is logically unset, but we are
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* keeping the struct around so as not to forget about its hook function(s).
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*/
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struct _variable
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{
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char *name;
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char *value;
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VariableSubstituteHook substitute_hook;
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VariableAssignHook assign_hook;
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struct _variable *next;
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};
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/* Data structure representing a set of variables */
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typedef struct _variable *VariableSpace;
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VariableSpace CreateVariableSpace(void);
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const char *GetVariable(VariableSpace space, const char *name);
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bool ParseVariableBool(const char *value, const char *name,
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bool *result);
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bool ParseVariableNum(const char *value, const char *name,
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int *result);
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void PrintVariables(VariableSpace space);
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bool SetVariable(VariableSpace space, const char *name, const char *value);
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bool SetVariableBool(VariableSpace space, const char *name);
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bool DeleteVariable(VariableSpace space, const char *name);
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void SetVariableHooks(VariableSpace space, const char *name,
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VariableSubstituteHook shook,
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VariableAssignHook ahook);
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bool VariableHasHook(VariableSpace space, const char *name);
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void PsqlVarEnumError(const char *name, const char *value, const char *suggestions);
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#endif /* VARIABLES_H */
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